Lead is a
chemical element
A chemical element is a species of atoms that have a given number of protons in their nuclei, including the pure substance consisting only of that species. Unlike chemical compounds, chemical elements cannot be broken down into simpler sub ...
with the
symbol
A symbol is a mark, sign, or word that indicates, signifies, or is understood as representing an idea, object, or relationship. Symbols allow people to go beyond what is known or seen by creating linkages between otherwise very different conc ...
Pb (from the
Latin
Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
) and
atomic number
The atomic number or nuclear charge number (symbol ''Z'') of a chemical element is the charge number of an atomic nucleus. For ordinary nuclei, this is equal to the proton number (''n''p) or the number of protons found in the nucleus of every ...
82. It is a
heavy metal that is
denser
Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek language, Greek letter Rho (letter), rho), although the Latin letter ''D'' ca ...
than most common materials. Lead is
soft and
malleable
Ductility is a mechanical property commonly described as a material's amenability to drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile stres ...
, and also has a relatively low
melting point
The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends ...
. When freshly cut, lead is a shiny gray with a hint of blue. It
tarnish
Tarnish is a thin layer of corrosion that forms over copper, brass, aluminum, magnesium, neodymium and other similar metals as their outermost layer undergoes a chemical reaction. Tarnish does not always result from the sole effects of oxygen in ...
es to a dull gray color when exposed to air. Lead has the highest atomic number of any
stable element
A stable is a building in which livestock, especially horses, are kept. It most commonly means a building that is divided into separate Stall (livestock), stalls for individual animals and livestock. There are many different types of stables ...
and three of its isotopes are endpoints of major nuclear
decay chain
In nuclear science, the decay chain refers to a series of radioactive decays of different radioactive decay products as a sequential series of transformations. It is also known as a "radioactive cascade". Most radioisotopes do not decay direct ...
s of heavier elements. Lead is toxic, even in small amounts, especially to children.
Lead is a relatively unreactive
post-transition metal
The metallic elements in the periodic table located between the transition metals and the chemically weak nonmetallic metalloids have received many names in the literature, such as ''post-transition metals'', ''poor metals'', ''other metals'', ...
. Its weak metallic character is illustrated by its
amphoteric
In chemistry, an amphoteric compound () is a molecule or ion that can react both as an acid and as a base. What exactly this can mean depends on which definitions of acids and bases are being used.
One type of amphoteric species are amphiproti ...
nature; lead and
lead oxide
Lead oxides are a group of inorganic compounds with formulas including lead (Pb) and oxygen (O).
Common lead oxides include:
* Lead(II) oxide, PbO, litharge (red), massicot (yellow)
* Lead(II,IV) oxide, Pb3O4, minium, ''red lead''
* Lead dioxide ...
s react with
acid
In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a sequ ...
s and
bases, and it tends to form
covalent bond
A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atoms ...
s.
Compounds of lead
Compounds of lead exist with lead in two main oxidation states: +2 and +4. The former is more common. Inorganic lead(IV) compounds are typically strong oxidants or exist only in highly acidic solutions.
Chemistry
Various oxidized forms of le ...
are usually found in the +2
oxidation state
In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...
rather than the +4 state common with lighter members of the
carbon group
The carbon group is a periodic table group consisting of carbon (C), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), and flerovium (Fl). It lies within the p-block.
In modern IUPAC notation, it is called group 14. In the field of semicond ...
. Exceptions are mostly limited to
organolead compound Organolead compounds are chemical compounds containing a chemical bond between carbon and lead. Organolead chemistry is the corresponding science. The first organolead compound was hexaethyldilead (Pb2(C2H5)6), first synthesized in 1858.''Main Grou ...
s. Like the lighter members of the group, lead tends to
bond with itself; it can form chains and polyhedral structures.
Since lead is easily extracted from its
ore
Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Retrieved 7 April 2 ...
s, prehistoric people in the Near East
were aware of it.
Galena
Galena, also called lead glance, is the natural mineral form of lead(II) sulfide (PbS). It is the most important ore of lead and an important source of silver.
Galena is one of the most abundant and widely distributed sulfide minerals. It cryst ...
is a principal ore of lead which often bears silver. Interest in silver helped initiate widespread extraction and use of lead in
ancient Rome
In modern historiography, ancient Rome refers to Roman civilisation from the founding of the city of Rome in the 8th century BC to the collapse of the Western Roman Empire in the 5th century AD. It encompasses the Roman Kingdom (753–509 B ...
. Lead production declined after the
fall of Rome
The fall of the Western Roman Empire (also called the fall of the Roman Empire or the fall of Rome) was the loss of central political control in the Western Roman Empire, a process in which the Empire failed to enforce its rule, and its vas ...
and did not reach comparable levels until the
Industrial Revolution
The Industrial Revolution was the transition to new manufacturing processes in Great Britain, continental Europe, and the United States, that occurred during the period from around 1760 to about 1820–1840. This transition included going f ...
. Lead played
a crucial role in the development of the
printing press
A printing press is a mechanical device for applying pressure to an inked surface resting upon a printing, print medium (such as paper or cloth), thereby transferring the ink. It marked a dramatic improvement on earlier printing methods in wh ...
, as
movable type
Movable type (US English; moveable type in British English) is the system and technology of printing and typography that uses movable components to reproduce the elements of a document (usually individual alphanumeric characters or punctuatio ...
could be relatively easily cast from lead alloys. In 2014, the annual global production of lead was about ten million tonnes, over half of which was from recycling. Lead's high density, low melting point,
ductility
Ductility is a mechanical property commonly described as a material's amenability to drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile stres ...
and relative inertness to
oxidation
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...
make it useful. These properties, combined with its relative abundance and low cost, resulted in its extensive use in construction, plumbing,
batteries
Battery most often refers to:
* Electric battery, a device that provides electrical power
* Battery (crime), a crime involving unlawful physical contact
Battery may also refer to:
Energy source
*Automotive battery, a device to provide power t ...
, bullets and
shot
Shot may refer to:
Arts, entertainment, and media
* ''Shot'' (album), by The Jesus Lizard
*''Shot, Illusion, New God'', an EP by Gruntruck
*''Shot Rev 2.0'', a video album by The Sisters of Mercy
* "Shot" (song), by The Rasmus
* ''Shot'' (2017 fi ...
, weights,
solder
Solder (; NA: ) is a fusible metal alloy used to create a permanent bond between metal workpieces. Solder is melted in order to wet the parts of the joint, where it adheres to and connects the pieces after cooling. Metals or alloys suitable ...
s,
pewter
Pewter () is a malleable metal alloy consisting of tin (85–99%), antimony (approximately 5–10%), copper (2%), bismuth, and sometimes silver. Copper and antimony (and in antiquity lead) act as hardeners, but lead may be used in lower grades of ...
s,
fusible alloy A fusible alloy is a metal alloy capable of being easily fused, i.e. easily meltable, at relatively low temperatures. Fusible alloys are commonly, but not necessarily, eutectic alloys.
Sometimes the term "fusible alloy" is used to describe alloys ...
s,
white paints,
leaded gasoline
Tetraethyllead (commonly styled tetraethyl lead), abbreviated TEL, is an organolead compound with the formula Pb( C2H5)4. It is a fuel additive, first being mixed with gasoline beginning in the 1920s as a patented octane rating booster that all ...
, and
radiation shield
Radiation protection, also known as radiological protection, is defined by the International Atomic Energy Agency (IAEA) as "The protection of people from harmful effects of exposure to ionizing radiation, and the means for achieving this". Exposur ...
ing.
Lead's toxicity became widely recognized in the late 19th century, although a number of well-educated ancient Greek and Roman writers were aware of this fact and even knew some of the symptoms of lead poisoning. Lead is a
neurotoxin
Neurotoxins are toxins that are destructive to nerve tissue (causing neurotoxicity). Neurotoxins are an extensive class of exogenous chemical neurological insultsSpencer 2000 that can adversely affect function in both developing and mature ner ...
that accumulates in soft tissues and bones; it damages the
nervous system
In biology, the nervous system is the highly complex part of an animal that coordinates its actions and sensory information by transmitting signals to and from different parts of its body. The nervous system detects environmental changes th ...
and interferes with the function of biological
enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...
s, causing
neurological disorder
A neurological disorder is any disorder of the nervous system. Structural, biochemical or electrical abnormalities in the brain, spinal cord or other nerves can result in a range of symptoms. Examples of symptoms include paralysis, muscle weakn ...
s ranging from behavioral problems to brain damage, and also affects general health, cardiovascular, and renal systems.
Physical properties
Atomic
A lead
atom
Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons.
Every solid, liquid, gas, and ...
has 82
electron
The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family,
and are generally thought to be elementary particles because they have no kn ...
s, arranged in an
electron configuration
In atomic physics and quantum chemistry, the electron configuration is the distribution of electrons of an atom or molecule (or other physical structure) in atomic or molecular orbitals. For example, the electron configuration of the neon atom ...
of [
Xe]4f
145d
106s
26p
2. The sum of lead's first and second
ionization energies
Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule i ...
—the total energy required to remove the two 6p electrons—is close to that of
tin
Tin is a chemical element with the symbol Sn (from la, stannum) and atomic number 50. Tin is a silvery-coloured metal.
Tin is soft enough to be cut with little force and a bar of tin can be bent by hand with little effort. When bent, t ...
, lead's upper neighbor in the
carbon group
The carbon group is a periodic table group consisting of carbon (C), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), and flerovium (Fl). It lies within the p-block.
In modern IUPAC notation, it is called group 14. In the field of semicond ...
. This is unusual; ionization energies generally fall going down a group, as an element's outer electrons become more distant from the
nucleus
Nucleus ( : nuclei) is a Latin word for the seed inside a fruit. It most often refers to:
*Atomic nucleus, the very dense central region of an atom
*Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA
Nucle ...
, and more
shielded by smaller orbitals.
The similarity of ionization energies is caused by the
lanthanide contraction
The lanthanide contraction is the greater-than-expected decrease in atomic radii/ionic radii of the elements in the lanthanide series from atomic number 57, lanthanum, to 71, lutetium, which results in smaller than otherwise expected atomic rad ...
—the decrease in element
radii
In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...
from
lanthanum
Lanthanum is a chemical element with the symbol La and atomic number 57. It is a soft, ductile, silvery-white metal that tarnishes slowly when exposed to air. It is the eponym of the lanthanide series, a group of 15 similar elements between lantha ...
(atomic number 57) to
lutetium
Lutetium is a chemical element with the symbol Lu and atomic number 71. It is a silvery white metal, which resists corrosion in dry air, but not in moist air. Lutetium is the last element in the lanthanide series, and it is traditionally counted am ...
(71), and the relatively small radii of the elements from
hafnium
Hafnium is a chemical element with the symbol Hf and atomic number 72. A lustrous, silvery gray, tetravalent transition metal, hafnium chemically resembles zirconium and is found in many zirconium minerals. Its existence was predicted by Dmitri M ...
(72) onwards. This is due to poor shielding of the nucleus by the
lanthanide
The lanthanide () or lanthanoid () series of chemical elements comprises the 15 metallic chemical elements with atomic numbers 57–71, from lanthanum through lutetium. These elements, along with the chemically similar elements scandium and yttr ...
4f electrons. The sum of the first four ionization energies of lead exceeds that of tin, contrary to what
periodic trends
Periodic trends are specific patterns that are present in the periodic table that illustrate different aspects of a certain element. They were discovered by the Russian chemist Dmitri Mendeleev in the year 1863. Major periodic trends include atom ...
would predict.
Relativistic effects
Relativistic quantum chemistry combines relativistic mechanics with quantum chemistry to calculate elemental properties and structure, especially for the heavier elements of the periodic table. A prominent example is an explanation for the color of ...
, which become significant in heavier atoms, contribute to this behavior. One such effect is the
inert pair effect The inert-pair effect is the tendency of the two electrons in the outermost atomic ''s''-orbital to remain unshared in compounds of post-transition metals. The term ''inert-pair effect'' is often used in relation to the increasing stability of oxi ...
: the 6s electrons of lead become reluctant to participate in bonding, making the distance between nearest atoms in
crystalline
A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macrosc ...
lead unusually long.
Lead's lighter carbon group
congeners form stable or metastable
allotrope
Allotropy or allotropism () is the property of some chemical elements to exist in two or more different forms, in the same physical state, known as allotropes of the elements. Allotropes are different structural modifications of an element: the ...
s with the tetrahedrally coordinated and
covalently bonded
A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atoms ...
diamond cubic
The diamond cubic crystal structure is a repeating pattern of 8 atoms that certain materials may adopt as they solidify. While the first known example was diamond, other elements in group 14 also adopt this structure, including α-tin, the sem ...
structure. The energy levels of their outer
s- and
p-orbital
In atomic theory and quantum mechanics, an atomic orbital is a Function (mathematics), function describing the location and wave-like behavior of an electron in an atom. This function can be used to calculate the probability of finding any electr ...
s are close enough to allow mixing into four
hybrid
Hybrid may refer to:
Science
* Hybrid (biology), an offspring resulting from cross-breeding
** Hybrid grape, grape varieties produced by cross-breeding two ''Vitis'' species
** Hybridity, the property of a hybrid plant which is a union of two dif ...
sp
3 orbitals. In lead, the inert pair effect increases the separation between its s- and p-orbitals, and the gap cannot be overcome by the energy that would be released by extra bonds following hybridization. Rather than having a diamond cubic structure, lead forms
metallic bonds
Metallic bonding is a type of chemical bonding that arises from the electrostatic attractive force between conduction electrons (in the form of an electron cloud of delocalized electrons) and positively charged metal ions. It may be descri ...
in which only the p-electrons are delocalized and shared between the Pb
2+ ions. Lead consequently has a
face-centered cubic
In crystallography, the cubic (or isometric) crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals.
There are three main varieties of ...
structure like the similarly sized
divalent
In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with other atoms when it forms chemical compounds or molecules.
Description
The combining capacity, or affinity of an ...
metals
calcium
Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to ...
and
strontium
Strontium is the chemical element with the symbol Sr and atomic number 38. An alkaline earth metal, strontium is a soft silver-white yellowish metallic element that is highly chemically reactive. The metal forms a dark oxide layer when it is ex ...
.
Bulk
Pure lead has a bright, shiny gray appearance with a hint of blue. It tarnishes on contact with moist air and takes on a dull appearance, the hue of which depends on the prevailing conditions. Characteristic properties of lead include high
density
Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematical ...
, malleability, ductility, and high resistance to
corrosion
Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engine ...
due to
passivation.
![Lead-2](https://upload.wikimedia.org/wikipedia/commons/6/63/Lead-2.jpg)
Lead's close-packed face-centered cubic structure and high atomic weight result in a density of 11.34 g/cm
3, which is greater than that of common metals such as iron (7.87 g/cm
3), copper (8.93 g/cm
3), and
zinc
Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...
(7.14 g/cm
3). This density is the origin of the idiom ''to go over like a lead balloon''. Some rarer metals are denser:
tungsten
Tungsten, or wolfram, is a chemical element with the symbol W and atomic number 74. Tungsten is a rare metal found naturally on Earth almost exclusively as compounds with other elements. It was identified as a new element in 1781 and first isolat ...
and gold are both at 19.3 g/cm
3, and
osmium
Osmium (from Greek grc, ὀσμή, osme, smell, label=none) is a chemical element with the symbol Os and atomic number 76. It is a hard, brittle, bluish-white transition metal in the platinum group that is found as a trace element in alloys, mos ...
—the densest metal known—has a density of 22.59 g/cm
3, almost twice that of lead.
Lead is a very soft metal with a
Mohs hardness
The Mohs scale of mineral hardness () is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material.
The scale was introduced in 1812 by th ...
of 1.5; it can be scratched with a fingernail. It is quite malleable and somewhat ductile. The
bulk modulus
The bulk modulus (K or B) of a substance is a measure of how resistant to compression the substance is. It is defined as the ratio of the infinitesimal pressure increase to the resulting ''relative'' decrease of the volume.
Other moduli describe ...
of lead—a measure of its ease of compressibility—is 45.8
GPa
Grading in education is the process of applying standardized measurements for varying levels of achievements in a course. Grades can be assigned as letters (usually A through F), as a range (for example, 1 to 6), as a percentage, or as a numbe ...
. In comparison, that of aluminium is 75.2 GPa; copper 137.8 GPa; and
mild steel
Carbon steel is a steel with carbon content from about 0.05 up to 2.1 percent by weight. The definition of carbon steel from the American Iron and Steel Institute (AISI) states:
* no minimum content is specified or required for chromium, cobalt ...
160–169 GPa. Lead's
tensile strength
Ultimate tensile strength (UTS), often shortened to tensile strength (TS), ultimate strength, or F_\text within equations, is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials t ...
, at 12–17 MPa, is low (that of aluminium is 6 times higher, copper 10 times, and mild steel 15 times higher); it can be strengthened by adding small amounts of copper or
antimony
Antimony is a chemical element with the symbol Sb (from la, stibium) and atomic number 51. A lustrous gray metalloid, it is found in nature mainly as the sulfide mineral stibnite (Sb2S3). Antimony compounds have been known since ancient time ...
.
The melting point of lead—at 327.5 °C (621.5 °F)—is very low compared to most metals. Its
boiling point
The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor.
The boiling point of a liquid varies depending upon the surrounding envir ...
of 1749 °C (3180 °F) is the lowest among the carbon group elements. The
electrical resistivity
Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that measures how strongly it resists electric current. A low resistivity indicates a material that readily allows ...
of lead at 20 °C is 192
nanoohm-meters, almost an
order of magnitude
An order of magnitude is an approximation of the logarithm of a value relative to some contextually understood reference value, usually 10, interpreted as the base of the logarithm and the representative of values of magnitude one. Logarithmic dis ...
higher than those of other industrial metals (copper at ; gold ; and aluminium at ). Lead is a
superconductor at temperatures lower than 7.19
K; this is the highest
critical temperature
Critical or Critically may refer to:
*Critical, or critical but stable, medical states
**Critical, or intensive care medicine
*Critical juncture, a discontinuous change studied in the social sciences.
*Critical Software, a company specializing in ...
of all
type-I superconductor
The interior of a bulk superconductor cannot be penetrated by a weak magnetic field, a phenomenon known as the Meissner effect. When the applied magnetic field becomes too large, superconductivity breaks down. Superconductors can be divided int ...
s and the third highest of the elemental superconductors.
Isotopes
Natural lead consists of four stable
isotope
Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numbers) ...
s with mass numbers of 204, 206, 207, and 208, and traces of five short-lived radioisotopes. The high number of isotopes is consistent with lead's
atomic number
The atomic number or nuclear charge number (symbol ''Z'') of a chemical element is the charge number of an atomic nucleus. For ordinary nuclei, this is equal to the proton number (''n''p) or the number of protons found in the nucleus of every ...
being even. Lead has a
magic number of protons (82), for which the
nuclear shell model
In nuclear physics, atomic physics, and nuclear chemistry, the nuclear shell model is a model of the atomic nucleus which uses the Pauli exclusion principle to describe the structure of the nucleus in terms of energy levels. The first shell mod ...
accurately predicts an especially stable nucleus. Lead-208 has 126 neutrons, another magic number, which may explain why lead-208 is extraordinarily stable.
With its high atomic number, lead is the heaviest element whose natural isotopes are regarded as stable; lead-208 is the heaviest stable nucleus. (This distinction formerly fell to
bismuth
Bismuth is a chemical element with the Symbol (chemistry), symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings arsenic and antimony. Elemental ...
, with an atomic number of 83, until its only
primordial isotope
In geochemistry, geophysics and nuclear physics, primordial nuclides, also known as primordial isotopes, are nuclides found on Earth that have existed in their current form since before Earth was formed. Primordial nuclides were present in the ...
, bismuth-209, was found in 2003 to decay very slowly.) The four stable isotopes of lead could theoretically undergo
alpha decay
Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus) and thereby transforms or 'decays' into a different atomic nucleus, with a mass number that is reduced by four and an atom ...
to isotopes of
mercury
Mercury commonly refers to:
* Mercury (planet), the nearest planet to the Sun
* Mercury (element), a metallic chemical element with the symbol Hg
* Mercury (mythology), a Roman god
Mercury or The Mercury may also refer to:
Companies
* Merc ...
with a release of energy, but this has not been observed for any of them; their predicted half-lives range from 10
35 to 10
189 years (at least 10
25 times the current age of the universe).
Three of the stable isotopes are found in three of the four major
decay chains
In nuclear science, the decay chain refers to a series of radioactive decays of different radioactive decay products as a sequential series of transformations. It is also known as a "radioactive cascade". Most radioisotopes do not decay direc ...
: lead-206, lead-207, and lead-208 are the final decay products of uranium-238, uranium-235, and thorium-232, respectively. These decay chains are called the uranium chain, the actinium chain, and the thorium chain. Their isotopic concentrations in a natural rock sample depends greatly on the presence of these three parent uranium and thorium isotopes. For example, the relative abundance of lead-208 can range from 52% in normal samples to 90% in thorium ores; for this reason, the standard atomic weight of lead is given to only one decimal place. As time passes, the ratio of lead-206 and lead-207 to lead-204 increases, since the former two are supplemented by radioactive decay of heavier elements while the latter is not; this allows for
lead–lead dating
Lead–lead dating is a method for dating geological samples, normally based on 'whole-rock' samples of material such as granite. For most dating requirements it has been superseded by uranium–lead dating (U–Pb dating), but in certain speciali ...
. As uranium decays into lead, their relative amounts change; this is the basis for
uranium–lead dating
Uranium–lead dating, abbreviated U–Pb dating, is one of the oldest and most refined of the radiometric dating schemes. It can be used to date rocks that formed and crystallised from about 1 million years to over 4.5 billion years ago with routi ...
. Lead-207 exhibits
nuclear magnetic resonance
Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a strong constant magnetic field are perturbed by a weak oscillating magnetic field (in the near field) and respond by producing an electromagnetic signal with a ...
, a property that has been used to study its compounds in solution and solid state, including in human body.
![Holsinger Meteorite](https://upload.wikimedia.org/wikipedia/commons/5/58/Holsinger_Meteorite.jpg)
Apart from the stable isotopes, which make up almost all lead that exists naturally, there are
trace quantities of a few radioactive isotopes. One of them is lead-210; although it has a half-life of only 22.2 years, small quantities occur in nature because lead-210 is produced by a long decay series that starts with uranium-238 (that has been present for billions of years on Earth). Lead-211, −212, and −214 are present in the decay chains of uranium-235, thorium-232, and uranium-238, respectively, so traces of all three of these lead isotopes are found naturally. Minute traces of lead-209 arise from the very rare
cluster decay
Cluster decay, also named heavy particle radioactivity or heavy ion radioactivity, is a rare type of nuclear decay in which an atomic nucleus emits a small "cluster" of neutrons and protons, more than in an alpha particle, but less than a typic ...
of radium-223, one of the
daughter product
In nuclear physics, a decay product (also known as a daughter product, daughter isotope, radio-daughter, or daughter nuclide) is the remaining nuclide left over from radioactive decay. Radioactive decay often proceeds via a sequence of steps ( ...
s of natural uranium-235, and the decay chain of neptunium-237, traces of which are produced by
neutron capture
Neutron capture is a nuclear reaction in which an atomic nucleus and one or more neutrons collide and merge to form a heavier nucleus. Since neutrons have no electric charge, they can enter a nucleus more easily than positively charged protons, ...
in uranium ores. Lead-210 is particularly useful for helping to identify the ages of samples by measuring its ratio to lead-206 (both isotopes are present in a single decay chain).
In total, 43 lead isotopes have been synthesized, with mass numbers 178–220. Lead-205 is the most stable radioisotope, with a half-life of around 1.73 years. The second-most stable is lead-202, which has a half-life of about 52,500 years, longer than any of the natural trace radioisotopes.
Chemistry
![FlammenfärbungPb](https://upload.wikimedia.org/wikipedia/commons/0/03/Flammenf%C3%A4rbungPb.png)
Bulk lead exposed to moist air forms a protective layer of varying composition.
Lead(II) carbonate
Lead(II) carbonate is the chemical compound with the chemical formula . It is a white solid with several practical uses, despite its toxicity. It occurs naturally as the mineral cerussite.
Structure
Like all metal carbonates, lead(II) carbonate a ...
is a common constituent; the
sulfate
The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ar ...
or
chloride
The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride salts ...
may also be present in urban or maritime settings. This layer makes bulk lead effectively chemically inert in the air. Finely powdered lead, as with many metals, is
pyrophoric
A substance is pyrophoric (from grc-gre, πυροφόρος, , 'fire-bearing') if it ignites spontaneously in air at or below (for gases) or within 5 minutes after coming into contact with air (for liquids and solids). Examples are organolith ...
, and burns with a bluish-white flame.
Fluorine
Fluorine is a chemical element with the symbol F and atomic number 9. It is the lightest halogen and exists at standard conditions as a highly toxic, pale yellow diatomic gas. As the most electronegative reactive element, it is extremely reacti ...
reacts with lead at room temperature, forming
lead(II) fluoride
Lead(II) fluoride is the inorganic compound with the formula Pb F2. It is a white solid. It exists as both an orthorhombic and cubic forms.
Uses
Lead(II) fluoride is used in low melting glasses, in glass coatings to reflect infrared rays, ...
. The reaction with
chlorine
Chlorine is a chemical element with the Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate betwee ...
is similar but requires heating, as the resulting chloride layer diminishes the reactivity of the elements. Molten lead reacts with the
chalcogen
The chalcogens (ore forming) ( ) are the chemical elements in group 16 of the periodic table. This group is also known as the oxygen family. Group 16 consists of the elements oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the radioact ...
s to give lead(II) chalcogenides.
Lead metal resists
sulfuric and
phosphoric acid
Phosphoric acid (orthophosphoric acid, monophosphoric acid or phosphoric(V) acid) is a colorless, odorless phosphorus-containing solid, and inorganic compound with the chemical formula . It is commonly encountered as an 85% aqueous solution, w ...
but not
hydrochloric
Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid. It is a component of the gastric acid in the digestiv ...
or
nitric acid
Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitri ...
; the outcome depends on insolubility and subsequent passivation of the product salt. Organic acids, such as
acetic acid
Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main component ...
, dissolve lead in the presence of oxygen. Concentrated
alkali
In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a basic, ionic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a ...
s will dissolve lead and form
plumbite In chemistry, plumbite is the oxyanion or hydrated forms, or any salt containing this anion. In these salts, lead is in the oxidation state +2. It is the traditional term for the IUPAC name plumbate(II).
For example, lead(II) oxide (PbO) dissolves ...
s.
Inorganic compounds
Lead shows two main oxidation states: +4 and +2. The
tetravalent
In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with other atoms when it forms chemical compounds or molecules.
Description
The combining capacity, or affinity of an ...
state is common for the carbon group. The divalent state is rare for
carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent
In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...
and
silicon
Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic tab ...
, minor for germanium, important (but not prevailing) for tin, and is the more important of the two oxidation states for lead. This is attributable to
relativistic effects
Relativistic quantum chemistry combines relativistic mechanics with quantum chemistry to calculate elemental properties and structure, especially for the heavier elements of the periodic table. A prominent example is an explanation for the color of ...
, specifically the
inert pair effect The inert-pair effect is the tendency of the two electrons in the outermost atomic ''s''-orbital to remain unshared in compounds of post-transition metals. The term ''inert-pair effect'' is often used in relation to the increasing stability of oxi ...
, which manifests itself when there is a large difference in
electronegativity
Electronegativity, symbolized as , is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atom's electronegativity is affected by both its atomic number and the d ...
between lead and
oxide
An oxide () is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of −2. Most of the E ...
,
halide
In chemistry, a halide (rarely halogenide) is a binary chemical compound, of which one part is a halogen atom and the other part is an element or radical that is less electronegative (or more electropositive) than the halogen, to make a fluor ...
, or
nitride
In chemistry, a nitride is an inorganic compound of nitrogen. The "nitride" anion, N3- ion, is very elusive but compounds of nitride are numerous, although rarely naturally occuring. Some nitrides have a find applications, such as wear-resistant ...
anions, leading to a significant partial positive charge on lead. The result is a stronger contraction of the lead 6s orbital than is the case for the 6p orbital, making it rather inert in ionic compounds. The inert pair effect is less applicable to compounds in which lead forms covalent bonds with elements of similar electronegativity, such as carbon in organolead compounds. In these, the 6s and 6p orbitals remain similarly sized and sp
3 hybridization is still energetically favorable. Lead, like carbon, is predominantly tetravalent in such compounds.
There is a relatively large difference in the electronegativity of lead(II) at 1.87 and lead(IV) at 2.33. This difference marks the reversal in the trend of increasing stability of the +4 oxidation state going down the carbon group; tin, by comparison, has values of 1.80 in the +2 oxidation state and 1.96 in the +4 state.
Lead(II)
![Oxid_olovnatý](https://upload.wikimedia.org/wikipedia/commons/d/d6/Oxid_olovnat%C3%BD.JPG)
Lead(II) compounds are characteristic of the inorganic chemistry of lead. Even strong
oxidizing agent
An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or "Electron acceptor, accepts"/"receives" an electron from a (called the , , or ). In ot ...
s like fluorine and chlorine react with lead to give only PbF
2 and PbCl
2. Lead(II) ions are usually colorless in solution, and partially hydrolyze to form Pb(OH)
+ and finally
4(OH)4">b4(OH)4sup>4+ (in which the
hydroxyl
In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy ...
ions act as
bridging ligand
In coordination chemistry, a bridging ligand is a ligand that connects two or more atoms, usually metal ions. The ligand may be atomic or polyatomic. Virtually all complex organic compounds can serve as bridging ligands, so the term is usually r ...
s), but are not
reducing agent
In chemistry, a reducing agent (also known as a reductant, reducer, or electron donor) is a chemical species that "donates" an electron to an (called the , , , or ).
Examples of substances that are commonly reducing agents include the Earth meta ...
s as tin(II) ions are.
Techniques
Technique or techniques may refer to:
Music
* The Techniques, a Jamaican rocksteady vocal group of the 1960s
*Technique (band), a British female synth pop band in the 1990s
* ''Technique'' (album), by New Order, 1989
* ''Techniques'' (album), by M ...
for identifying the presence of the Pb
2+ ion in water generally rely on the precipitation of lead(II) chloride using dilute hydrochloric acid. As the chloride salt is sparingly soluble in water, in very dilute solutions the precipitation of lead(II) sulfide is instead achieved by bubbling
hydrogen sulfide
Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The unde ...
through the solution.
Lead monoxide
Lead(II) oxide, also called lead monoxide, is the inorganic compound with the molecular formula Pb O. PbO occurs in two polymorphs: litharge having a tetragonal crystal structure, and massicot having an orthorhombic crystal structure. Modern ap ...
exists in two
polymorphs,
litharge
Litharge (from Greek lithargyros, lithos (stone) + argyros (silver) ''λιθάργυρος'') is one of the natural mineral forms of lead(II) oxide, PbO. Litharge is a secondary mineral which forms from the oxidation of galena ores. It forms as coa ...
α-PbO (red) and
massicot
Massicot is lead (II) oxide mineral with an orthorhombic lattice structure.
Lead(II) oxide (formula: PbO) can occur in one of two lattice formats, orthorhombic and tetragonal. The tetragonal form is called litharge. PbO can be changed from massi ...
β-PbO (yellow), the latter being stable only above around 488 °C. Litharge is the most commonly used inorganic compound of lead. There is no lead(II) hydroxide; increasing the pH of solutions of lead(II) salts leads to hydrolysis and condensation.
Lead commonly reacts with heavier chalcogens.
Lead sulfide Lead sulfide refers to two compounds containing lead and sulfur:
*Lead(II) sulfide
Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is s ...
is a
semiconductor
A semiconductor is a material which has an electrical resistivity and conductivity, electrical conductivity value falling between that of a electrical conductor, conductor, such as copper, and an insulator (electricity), insulator, such as glas ...
, a
photoconductor
Photoconductivity is an optical and electrical phenomenon in which a material becomes more electrically conductive due to the absorption of electromagnetic radiation such as visible light, ultraviolet light, infrared light, or gamma radiation.
Whe ...
, and an extremely sensitive
infrared radiation detector. The other two chalcogenides,
lead selenide
Lead selenide (PbSe), or lead(II) selenide, a selenide of lead, is a semiconductor material. It forms cubic crystals of the NaCl structure; it has a direct bandgap of 0.27 eV at room temperature. (Note that incorrectly identifies PbSe and o ...
and
lead telluride
Lead telluride is a compound of lead and tellurium (PbTe). It crystallizes in the NaCl crystal structure with Pb atoms occupying the cation and Te forming the anionic lattice. It is a narrow gap semiconductor with a band gap of 0.32 eV. It occurs ...
, are likewise photoconducting. They are unusual in that their color becomes lighter going down the group.
![Red-lead-unit-cell-3D-balls](https://upload.wikimedia.org/wikipedia/commons/0/0d/Red-lead-unit-cell-3D-balls.png)
Lead dihalides are well-characterized; this includes the diastatide and mixed halides, such as PbFCl. The relative insolubility of the latter forms a useful basis for the
gravimetric
Gravimetry is the measurement of the strength of a gravitational field. Gravimetry may be used when either the magnitude of a gravitational field or the properties of matter responsible for its creation are of interest.
Units of measurement
Gr ...
determination of fluorine. The difluoride was the first solid
ionically conducting compound to be discovered (in 1834, by
Michael Faraday
Michael Faraday (; 22 September 1791 – 25 August 1867) was an English scientist who contributed to the study of electromagnetism and electrochemistry. His main discoveries include the principles underlying electromagnetic inducti ...
). The other dihalides decompose on exposure to ultraviolet or visible light, especially the diiodide. Many lead(II)
pseudohalides are known, such as the
cyanide
Cyanide is a naturally occurring, rapidly acting, toxic chemical that can exist in many different forms.
In chemistry, a cyanide () is a chemical compound that contains a functional group. This group, known as the cyano group, consists of ...
,
cyanate
Cyanate is an anion with the structural formula , usually written . It also refers to any salt containing it, such as ammonium cyanate.
It is an isomer of the much less stable fulminate anion .William R. Martin and David W. Ball (2019): "Small ...
, and
thiocyanate
Thiocyanate (also known as rhodanide) is the anion . It is the conjugate base of thiocyanic acid. Common derivatives include the colourless salts potassium thiocyanate and sodium thiocyanate. Mercury(II) thiocyanate was formerly used in pyrot ...
. Lead(II) forms an extensive variety of halide
coordination complex
A coordination complex consists of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as ''ligands'' or complexing agents. Many ...
es, such as
4">bCl4sup>2−,
6">bCl6sup>4−, and the
2Cl9">b2Cl9sub>''n''
5''n''− chain anion.
Lead(II) sulfate
Lead(II) sulfate (PbSO4) is a white solid, which appears white in microcrystalline form. It is also known as ''fast white'', ''milk white'', ''sulfuric acid lead salt'' or ''anglesite''.
It is often seen in the plates/electrodes of car batteries, ...
is insoluble in water, like the sulfates of other heavy divalent
cation
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
s. Lead(II) nitrate and
lead(II) acetate
Lead(II) acetate (Pb(CH3COO)2), also known as lead acetate, lead diacetate, plumbous acetate, sugar of lead, lead sugar, salt of Saturn, or Goulard's powder, is a white crystalline chemical compound with a slightly sweet taste. Like many other le ...
are very soluble, and this is exploited in the synthesis of other lead compounds.
Lead(IV)
Few inorganic lead(IV) compounds are known. They are only formed in highly oxidizing solutions and do not normally exist under standard conditions. Lead(II) oxide gives a mixed oxide on further oxidation, Pb
3O
4. It is described as
lead(II,IV) oxide
Lead(II,IV) oxide, also called red lead or minium, is the inorganic compound with the formula Pb3O4. A bright red or orange solid, it is used as pigment, in the manufacture of batteries, and rustproof primer paints. It is an example of a mixed v ...
, or structurally 2PbO·PbO
2, and is the best-known mixed valence lead compound.
Lead dioxide
Lead(IV) oxide is the inorganic compound with the formula PbO2. It is an oxide where lead is in an oxidation state of +4. It is a dark-brown solid which is insoluble in water. It exists in two crystalline forms. It has several important applicatio ...
is a strong oxidizing agent, capable of oxidizing hydrochloric acid to chlorine gas. This is because the expected PbCl
4 that would be produced is unstable and spontaneously decomposes to PbCl
2 and Cl
2. Analogously to
lead monoxide
Lead(II) oxide, also called lead monoxide, is the inorganic compound with the molecular formula Pb O. PbO occurs in two polymorphs: litharge having a tetragonal crystal structure, and massicot having an orthorhombic crystal structure. Modern ap ...
, lead dioxide is capable of forming
plumbate
In chemistry, a plumbate often refers to compounds that can be viewed as derivatives of the hypothetical anion. The term also refers to any anion of lead or any salt thereof. So the term is vague and somewhat archaic.
Examples Halides
Salts of , ...
anions.
Lead disulfide
Lead(IV) sulfide is a chemical compound with the formula Pb S2. This material is generated by the reaction of the more common lead(II) sulfide, PbS, with sulfur at >600 °C and at high pressures. PbS2, like the related tin(IV) sulfide SnS2, crysta ...
and lead diselenide are only stable at high pressures.
Lead tetrafluoride
Lead tetrafluoride is a compound of lead and fluorine. The yellow solid (melting point 600 °C) is the only room-temperature stable tetrahalide of lead. Lead tetrafluoride is isostructural with tin(IV) fluoride and contains planar layers of ...
, a yellow crystalline powder, is stable, but less so than the
difluoride.
Lead tetrachloride
Lead tetrachloride, also known as lead(IV) chloride, has the molecular formula PbCl4. It is a yellow, oily liquid which is stable below 0 °C, and decomposes at 50 °C. It has a tetrahedral configuration, with lead as the central atom. ...
(a yellow oil) decomposes at room temperature, lead tetrabromide is less stable still, and the existence of lead tetraiodide is questionable.
Other oxidation states
![Nonaplumbide-anion-from-xtal-3D-balls](https://upload.wikimedia.org/wikipedia/commons/5/54/Nonaplumbide-anion-from-xtal-3D-balls.png)
Some lead compounds exist in formal oxidation states other than +4 or +2. Lead(III) may be obtained, as an intermediate between lead(II) and lead(IV), in larger organolead complexes; this oxidation state is not stable, as both the lead(III) ion and the larger complexes containing it are
radicals. The same applies for lead(I), which can be found in such radical species.
Numerous mixed lead(II,IV) oxides are known. When PbO
2 is heated in air, it becomes Pb
12O
19 at 293 °C, Pb
12O
17 at 351 °C, Pb
3O
4 at 374 °C, and finally PbO at 605 °C. A further
sesquioxide
A sesquioxide is an oxide of an element (or radical), where the ratio between the number of atoms of that element and the number of atoms of oxygen is 2:3. For example, aluminium oxide and phosphorus(III) oxide are sesquioxides.
Many sesquioxid ...
, Pb
2O
3, can be obtained at high pressure, along with several non-stoichiometric phases. Many of them show defective
fluorite
Fluorite (also called fluorspar) is the mineral form of calcium fluoride, CaF2. It belongs to the halide minerals. It crystallizes in isometric cubic habit, although octahedral and more complex isometric forms are not uncommon.
The Mohs sca ...
structures in which some oxygen atoms are replaced by vacancies: PbO can be considered as having such a structure, with every alternate layer of oxygen atoms absent.
Negative oxidation states can occur as
Zintl phases
In chemistry, a Zintl phase is a product of a reaction between a group 1 ( alkali metal) or group 2 (alkaline earth metal) and main group metal or metalloid (from groups 13, 14, 15, or 16). It is characterized by intermediate metallic/ ionic bon ...
, as either free lead anions, as in Ba
2Pb, with lead formally being lead(−IV), or in oxygen-sensitive ring-shaped or polyhedral cluster ions such as the
trigonal bipyramidal
In chemistry, a trigonal bipyramid formation is a molecular geometry with one atom at the center and 5 more atoms at the corners of a triangular bipyramid. This is one geometry for which the bond angles surrounding the central atom are not identi ...
Pb
52− ion, where two lead atoms are lead(−I) and three are lead(0). In such anions, each atom is at a polyhedral vertex and contributes two electrons to each covalent bond along an edge from their sp
3 hybrid orbitals, the other two being an external
lone pair
In chemistry, a lone pair refers to a pair of valence electrons that are not shared with another atom in a covalent bondIUPAC ''Gold Book'' definition''lone (electron) pair''/ref> and is sometimes called an unshared pair or non-bonding pair. Lone ...
. They may be made in
liquid ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wast ...
via the reduction of lead by
sodium
Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable iso ...
.
Organolead
![Tetraethyllead-3D-balls](https://upload.wikimedia.org/wikipedia/commons/d/df/Tetraethyllead-3D-balls.png)
Lead can form
multiply-bonded chains, a property it shares with its lighter
homologs
A couple of homologous chromosomes, or homologs, are a set of one maternal and one paternal chromosome that pair up with each other inside a cell during fertilization. Homologs have the same genes in the same locus (genetics), loci where they pr ...
in the carbon group. Its capacity to do so is much less because the Pb–Pb
bond energy
In chemistry, bond energy (''BE''), also called the mean bond enthalpy or average bond enthalpy is the measure of bond strength in a chemical bond. IUPAC defines bond energy as the average value of the gas-phase bond-dissociation energy (usually at ...
is over three and a half times lower than that of the C–C bond. With itself, lead can build metal–metal bonds of an order up to three. With carbon, lead forms organolead compounds similar to, but generally less stable than, typical organic compounds (due to the Pb–C bond being rather weak). This makes the
organometallic chemistry
Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and so ...
of lead far less wide-ranging than that of tin. Lead predominantly forms organolead(IV) compounds, even when starting with inorganic lead(II) reactants; very few organolead(II) compounds are known. The most well-characterized exceptions are Pb
3)2">H(SiMe3)2sub>2 and Pb(''η''
5-C
5H
5)
2.
The lead analog of the simplest
organic compound
In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...
,
methane
Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Eart ...
, is
plumbane
Plumbane, PbH4, is a metal hydride and group 14 hydride composed of lead and hydrogen. Plumbane is not well characterized or well known, and it is thermodynamically unstable with respect to the loss of a hydrogen atom. Derivatives of plumbane inclu ...
. Plumbane may be obtained in a reaction between metallic lead and
atomic hydrogen
A hydrogen atom is an atom of the chemical element hydrogen. The electrically neutral atom contains a single positively charged proton and a single negatively charged electron bound to the nucleus by the Coulomb force. Atomic hydrogen constit ...
. Two simple derivatives,
tetramethyllead
Tetramethyllead, also called tetra methyllead and lead tetramethyl, is a chemical compound used as an antiknock additive for gasoline. Its use is being phased out for environmental considerations.
The National Institute for Occupational Safety a ...
and
tetraethyllead
Tetraethyllead (commonly styled tetraethyl lead), abbreviated TEL, is an organolead compound with the formula Pb( C2H5)4. It is a fuel additive, first being mixed with gasoline beginning in the 1920s as a patented octane rating booster that al ...
, are the best-known
organolead Organolead compounds are chemical compounds containing a chemical bond between carbon and lead. Organolead chemistry is the corresponding science. The first organolead compound was hexaethyldilead (Pb2(C2H5)6), first synthesized in 1858.''Main Grou ...
compounds. These compounds are relatively stable: tetraethyllead only starts to decompose if heated or if exposed to sunlight or ultraviolet light. With sodium metal, lead readily forms an equimolar alloy that reacts with
alkyl halide
The haloalkanes (also known as halogenoalkanes or alkyl halides) are alkanes containing one or more halogen substituents. They are a subset of the general class of halocarbons, although the distinction is not often made. Haloalkanes are widely ...
s to form
organometallic
Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and so ...
compounds such as tetraethyllead. The oxidizing nature of many organolead compounds is usefully exploited:
lead tetraacetate
Lead(IV) acetate or lead tetraacetate is an organometallic compound with chemical formula . It is a colorless solid that is soluble in nonpolar, organic solvents, indicating that it is not a salt. It is degraded by moisture and is typically store ...
is an important laboratory reagent for oxidation in organic synthesis. Tetraethyllead, once added to gasoline, was produced in larger quantities than any other organometallic compound. Other organolead compounds are less chemically stable. For many organic compounds, a lead analog does not exist.
Origin and occurrence
In space
Lead's per-particle abundance in the
Solar System
The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...
is 0.121
ppb (parts per billion). This figure is two and a half times higher than that of
platinum
Platinum is a chemical element with the symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name originates from Spanish , a diminutive of "silver".
Platinu ...
, eight times more than mercury, and seventeen times more than gold. The amount of lead in the
universe
The universe is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy. The Big Bang theory is the prevailing cosmological description of the development of the universe. Acc ...
is slowly increasing as most heavier atoms (all of which are unstable) gradually decay to lead. The abundance of lead in the Solar System since its formation 4.5 billion years ago has increased by about 0.75%. The solar system abundances table shows that lead, despite its relatively high atomic number, is more prevalent than most other elements with atomic numbers greater than 40.
Primordial lead—which comprises the isotopes lead-204, lead-206, lead-207, and lead-208—was mostly created as a result of repetitive neutron capture processes occurring in stars. The two main modes of capture are the
s- and
r-process
In nuclear astrophysics, the rapid neutron-capture process, also known as the ''r''-process, is a set of nuclear reactions that is responsible for the creation of approximately half of the atomic nuclei heavier than iron, the "heavy elements", ...
es.
In the s-process (s is for "slow"), captures are separated by years or decades, allowing less stable nuclei to undergo
beta decay
In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which a beta particle (fast energetic electron or positron) is emitted from an atomic nucleus, transforming the original nuclide to an isobar of that nuclide. For ...
. A stable thallium-203 nucleus can capture a neutron and become thallium-204; this undergoes beta decay to give stable lead-204; on capturing another neutron, it becomes lead-205, which has a half-life of around 15 million years. Further captures result in lead-206, lead-207, and lead-208. On capturing another neutron, lead-208 becomes lead-209, which quickly decays into bismuth-209. Bismuth-209 is also radioactive and eventually decays into thallium-205 if left unperturbed. On capturing another neutron, bismuth-209 becomes bismuth-210, and this beta decays to polonium-210, which alpha decays to lead-206. The cycle hence ends at lead-206, lead-207, lead-208, and thallium-205.
![S-R-processes-atomic-mass-201-to-210](https://upload.wikimedia.org/wikipedia/commons/6/6b/S-R-processes-atomic-mass-201-to-210.svg)
In the r-process (r is for "rapid"), captures happen faster than nuclei can decay. This occurs in environments with a high neutron density, such as a
supernova
A supernova is a powerful and luminous explosion of a star. It has the plural form supernovae or supernovas, and is abbreviated SN or SNe. This transient astronomical event occurs during the last evolutionary stages of a massive star or when ...
or the merger of two
neutron star
A neutron star is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially metal-rich. Except for black holes and some hypothetical objects (e.g. white ...
s. The neutron flux involved may be on the order of 10
22 neutrons per square centimeter per second. The r-process does not form as much lead as the s-process. It tends to stop once neutron-rich nuclei reach 126 neutrons. At this point, the neutrons are arranged in complete shells in the atomic nucleus, and it becomes harder to energetically accommodate more of them. When the neutron flux subsides, these nuclei beta decay into stable isotopes of osmium,
iridium
Iridium is a chemical element with the symbol Ir and atomic number 77. A very hard, brittle, silvery-white transition metal of the platinum group, it is considered the second-densest naturally occurring metal (after osmium) with a density of ...
, and platinum.
On Earth
Lead is classified as a
chalcophile
The Goldschmidt classification,
developed by Victor Goldschmidt (1888–1947), is a geochemical classification which groups the chemical elements within the Earth according to their preferred host phases into lithophile (Rock (geology), rock-lovi ...
under the
Goldschmidt classification
The Goldschmidt classification,
developed by Victor Goldschmidt (1888–1947), is a geochemical classification which groups the chemical elements within the Earth according to their preferred host phases into lithophile (rock-loving), siderophile ...
, meaning it is generally found combined with sulfur. It rarely occurs in its
native
Native may refer to:
People
* Jus soli, citizenship by right of birth
* Indigenous peoples, peoples with a set of specific rights based on their historical ties to a particular territory
** Native Americans (disambiguation)
In arts and entert ...
, metallic form. Many lead minerals are relatively light and, over the course of the Earth's history, have remained in the
crust instead of sinking deeper into the Earth's interior. This accounts for lead's relatively high
crustal abundance
The abundance of elements in Earth's crust is shown in tabulated form with the estimated crustal abundance for each chemical element shown as mg/kg, or parts per million (ppm) by mass (10,000 ppm = 1%).
Estimates of elemental abundance are diff ...
of 14 ppm; it is the 38th most
abundant element in the crust.
The main lead-bearing mineral is
galena
Galena, also called lead glance, is the natural mineral form of lead(II) sulfide (PbS). It is the most important ore of lead and an important source of silver.
Galena is one of the most abundant and widely distributed sulfide minerals. It cryst ...
(PbS), which is mostly found with zinc ores. Most other lead minerals are related to galena in some way;
boulangerite
Boulangerite is an uncommon monoclinic orthorhombic sulfosalt mineral, lead antimony sulfide, formula Pb5Sb4S11. It was named in 1837 in honor of French mining engineer Charles Boulanger (1810–1849),http://www.mindat.org/min-738.html Mindat and ...
, Pb
5Sb
4S
11, is a mixed sulfide derived from galena;
anglesite
Anglesite is a lead sulfate mineral with the chemical formula PbSO4. It occurs as an oxidation product of primary lead sulfide ore, galena. Anglesite occurs as prismatic orthorhombic crystals and earthy masses, and is isomorphous with barite and ...
, PbSO
4, is a product of galena oxidation; and
cerussite
Cerussite (also known as lead carbonate or white lead ore) is a mineral consisting of lead carbonate (PbCO3), and is an important ore of lead. The name is from the Latin ''cerussa'', white lead. ''Cerussa nativa'' was mentioned by Conrad Gessner ...
or white lead ore, PbCO
3, is a decomposition product of galena.
Arsenic
Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, but ...
, tin, antimony, silver, gold, copper, and bismuth are common impurities in lead minerals.
![Elemental abundances](https://upload.wikimedia.org/wikipedia/commons/0/09/Elemental_abundances.svg)
World lead resources exceed two billion tons. Significant deposits are located in Australia, China, Ireland, Mexico, Peru, Portugal, Russia, and the United States. Global reserves—resources that are economically feasible to extract—totaled 88 million tons in 2016, of which Australia had 35 million, China 17 million, and Russia 6.4 million.
Typical background concentrations of lead do not exceed 0.1 μg/m
3 in the atmosphere; 100 mg/kg in soil; 4 mg/kg in vegetation and 5 μg/L in freshwater and seawater.
Etymology
The modern English word ''lead'' is of Germanic origin; it comes from the
Middle English
Middle English (abbreviated to ME) is a form of the English language that was spoken after the Norman conquest of 1066, until the late 15th century. The English language underwent distinct variations and developments following the Old English p ...
and
Old English
Old English (, ), or Anglo-Saxon, is the earliest recorded form of the English language, spoken in England and southern and eastern Scotland in the early Middle Ages. It was brought to Great Britain by Anglo-Saxon settlement of Britain, Anglo ...
(with the
macron above the "e" signifying that the vowel sound of that letter is long). The Old English word is derived from the hypothetical reconstructed
Proto-Germanic
Proto-Germanic (abbreviated PGmc; also called Common Germanic) is the reconstructed proto-language of the Germanic branch of the Indo-European languages.
Proto-Germanic eventually developed from pre-Proto-Germanic into three Germanic branc ...
('lead'). According to linguistic theory, this word bore descendants in multiple Germanic languages of exactly the same meaning.
There is no consensus on the origin of the Proto-Germanic . One hypothesis suggests it is derived from
Proto-Indo-European
Proto-Indo-European (PIE) is the reconstructed common ancestor of the Indo-European language family. Its proposed features have been derived by linguistic reconstruction from documented Indo-European languages. No direct record of Proto-Indo-E ...
('lead'; capitalization of the vowel is equivalent to the macron). Another hypothesis suggests it is borrowed from
Proto-Celtic
Proto-Celtic, or Common Celtic, is the ancestral proto-language of all known Celtic languages, and a descendant of Proto-Indo-European. It is not attested in writing but has been partly Linguistic reconstruction, reconstructed through the compar ...
('lead'). This word is related to the
Latin
Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
, which gave the element its
chemical symbol
Chemical symbols are the abbreviations used in chemistry for chemical elements, functional groups and chemical compounds. Element symbols for chemical elements normally consist of one or two letters from the Latin alphabet and are written with th ...
''Pb''. The word is thought to be the origin of Proto-Germanic (which also means 'lead'), from which stemmed the German .
The name of the chemical element is not related to the verb of the same spelling, which is derived from Proto-Germanic ('to lead').
History
Prehistory and early history
![Lead production graph](https://upload.wikimedia.org/wikipedia/commons/5/56/Lead_production_graph.svg)
Metallic lead beads
dating back to 7000–6500 BCE have been found in
Asia Minor
Anatolia, tr, Anadolu Yarımadası), and the Anatolian plateau, also known as Asia Minor, is a large peninsula in Western Asia and the westernmost protrusion of the Asian continent. It constitutes the major part of modern-day Turkey. The re ...
and may represent the first example of metal
smelting
Smelting is a process of applying heat to ore, to extract a base metal. It is a form of extractive metallurgy. It is used to extract many metals from their ores, including silver, iron, copper, and other base metals. Smelting uses heat and a ch ...
. At that time lead had few (if any) applications due to its softness and dull appearance. The major reason for the spread of lead production was its association with silver, which may be obtained by burning galena (a common lead mineral). The
Ancient Egyptians were the first to use lead minerals in cosmetics, an application that spread to
Ancient Greece
Ancient Greece ( el, Ἑλλάς, Hellás) was a northeastern Mediterranean civilization, existing from the Greek Dark Ages of the 12th–9th centuries BC to the end of classical antiquity ( AD 600), that comprised a loose collection of cult ...
and beyond; the Egyptians may have used lead for sinkers in fishing nets,
glazes, glasses,
enamels, and for ornaments. Various civilizations of the
Fertile Crescent
The Fertile Crescent ( ar, الهلال الخصيب) is a crescent-shaped region in the Middle East, spanning modern-day Iraq, Syria, Lebanon, Israel, Palestine and Jordan, together with the northern region of Kuwait, southeastern region of ...
used lead as a writing material, as
coins
A coin is a small, flat (usually depending on the country or value), round piece of metal or plastic used primarily as a medium of exchange or legal tender. They are standardized in weight, and produced in large quantities at a mint in order to ...
, and as a construction material. Lead was used in the
Ancient Chinese royal court as a
stimulant
Stimulants (also often referred to as psychostimulants or colloquially as uppers) is an overarching term that covers many drugs including those that increase activity of the central nervous system and the body, drugs that are pleasurable and inv ...
, as currency, and as a
contraceptive
Birth control, also known as contraception, anticonception, and fertility control, is the use of methods or devices to prevent unwanted pregnancy. Birth control has been used since ancient times, but effective and safe methods of birth contr ...
; the
Indus Valley civilization
The Indus Valley Civilisation (IVC), also known as the Indus Civilisation was a Bronze Age civilisation in the northwestern regions of South Asia, lasting from 3300 BCE to 1300 BCE, and in its mature form 2600 BCE to 1900&n ...
and the
Mesoamerica
Mesoamerica is a historical region and cultural area in southern North America and most of Central America. It extends from approximately central Mexico through Belize, Guatemala, El Salvador, Honduras, Nicaragua, and northern Costa Rica. W ...
ns used it for making amulets; and the eastern and southern African peoples used lead in
wire drawing
Wire drawing is a metalworking process used to reduce the cross-section of a wire by pulling the wire through a single, or series of, drawing die(s). There are many applications for wire drawing, including electrical wiring, cables, tension-lo ...
.
Classical era
Because silver was extensively used as a decorative material and an exchange medium, lead deposits came to be worked in Asia Minor from 3000 BCE; later, lead deposits were developed in the
Aegean and
Laurion
Laurium or Lavrio ( ell, Λαύριο; grc, Λαύρειον (later ); before early 11th century BC: Θορικός ''Thorikos''; from Middle Ages until 1908: Εργαστήρια ''Ergastiria'') is a town in southeastern part of Attica, Greec ...
. These three regions collectively dominated production of mined lead until c. 1200 BCE. Beginning circa 2000 BCE, the
Phoenicia
Phoenicia () was an ancient thalassocratic civilization originating in the Levant region of the eastern Mediterranean, primarily located in modern Lebanon. The territory of the Phoenician city-states extended and shrank throughout their histor ...
ns worked deposits in the
Iberian peninsula
The Iberian Peninsula (),
**
* Aragonese and Occitan: ''Peninsula Iberica''
**
**
* french: Péninsule Ibérique
* mwl, Península Eibérica
* eu, Iberiar penintsula also known as Iberia, is a peninsula in southwestern Europe, defi ...
; by 1600 BCE, lead mining existed in
Cyprus
Cyprus ; tr, Kıbrıs (), officially the Republic of Cyprus,, , lit: Republic of Cyprus is an island country located south of the Anatolian Peninsula in the eastern Mediterranean Sea. Its continental position is disputed; while it is geo ...
, Greece, and
Sardinia
Sardinia ( ; it, Sardegna, label=Italian, Corsican and Tabarchino ; sc, Sardigna , sdc, Sardhigna; french: Sardaigne; sdn, Saldigna; ca, Sardenya, label=Algherese and Catalan) is the second-largest island in the Mediterranean Sea, after ...
.
Rome's territorial expansion in Europe and across the Mediterranean, and its development of mining, led to it becoming the greatest producer of lead during the
classical era
Classical antiquity (also the classical era, classical period or classical age) is the period of cultural history between the 8th century BC and the 5th century AD centred on the Mediterranean Sea, comprising the interlocking civilizations of ...
, with an estimated annual output peaking at 80,000 tonnes. Like their predecessors, the Romans obtained lead mostly as a by-product of silver smelting.
Lead mining
Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, l ...
occurred in Central Europe,
Britain
Britain most often refers to:
* The United Kingdom, a sovereign state in Europe comprising the island of Great Britain, the north-eastern part of the island of Ireland and many smaller islands
* Great Britain, the largest island in the United King ...
, the
Balkans
The Balkans ( ), also known as the Balkan Peninsula, is a geographical area in southeastern Europe with various geographical and historical definitions. The region takes its name from the Balkan Mountains that stretch throughout the who ...
,
Greece
Greece,, or , romanized: ', officially the Hellenic Republic, is a country in Southeast Europe. It is situated on the southern tip of the Balkans, and is located at the crossroads of Europe, Asia, and Africa. Greece shares land borders with ...
,
Anatolia
Anatolia, tr, Anadolu Yarımadası), and the Anatolian plateau, also known as Asia Minor, is a large peninsula in Western Asia and the westernmost protrusion of the Asian continent. It constitutes the major part of modern-day Turkey. The re ...
, and
Hispania
Hispania ( la, Hispānia , ; nearly identically pronounced in Spanish, Portuguese, Catalan, and Italian) was the Roman name for the Iberian Peninsula and its provinces. Under the Roman Republic, Hispania was divided into two provinces: Hispania ...
, the latter accounting for 40% of world production.
Lead tablets were commonly used as a material for letters.
Lead coffins
Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, l ...
, cast in flat sand forms, with interchangeable motifs to suit the faith of the deceased were used in ancient
Judea
Judea or Judaea ( or ; from he, יהודה, Hebrew language#Modern Hebrew, Standard ''Yəhūda'', Tiberian vocalization, Tiberian ''Yehūḏā''; el, Ἰουδαία, ; la, Iūdaea) is an ancient, historic, Biblical Hebrew, contemporaneous L ...
. Lead was used to make sling bullets from the 5th century BC. In Roman times, lead sling bullets were amply used, and were effective at a distance of between 100 and 150 meters. The Balearic slingers, used as mercenaries in Carthaginian and Roman armies, were famous for their shooting distance and accuracy.
![Grosvenor Museums - Wasserröhren](https://upload.wikimedia.org/wikipedia/commons/a/a3/Grosvenor_Museums_-_Wasserr%C3%B6hren.jpg)
Lead was used for making
water pipe
Plumbing is any system that conveys fluids for a wide range of applications. Plumbing uses pipes, valves, plumbing fixtures, tanks, and other apparatuses to convey fluids. Heating and cooling (HVAC), waste removal, and potable water delivery ...
s in the
Roman Empire
The Roman Empire ( la, Imperium Romanum ; grc-gre, Βασιλεία τῶν Ῥωμαίων, Basileía tôn Rhōmaíōn) was the post-Republican period of ancient Rome. As a polity, it included large territorial holdings around the Mediterr ...
; the
Latin
Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
word for the metal, , is the origin of the English word "plumbing". Its ease of working, its low melting point enabling the easy fabrication of completely waterproof welded joints, and its resistance to corrosion ensured its widespread use in other applications, including pharmaceuticals, roofing, currency, and warfare. Writers of the time, such as
Cato the Elder
Marcus Porcius Cato (; 234–149 BC), also known as Cato the Censor ( la, Censorius), the Elder and the Wise, was a Roman soldier, senator, and historian known for his conservatism and opposition to Hellenization. He was the first to write histo ...
,
Columella
Lucius Junius Moderatus Columella (; Arabic: , 4 – ) was a prominent writer on agriculture in the Roman Empire.
His ' in twelve volumes has been completely preserved and forms an important source on Roman agriculture, together with the wo ...
, and
Pliny the Elder
Gaius Plinius Secundus (AD 23/2479), called Pliny the Elder (), was a Roman author, naturalist and natural philosopher, and naval and army commander of the early Roman Empire, and a friend of the emperor Vespasian. He wrote the encyclopedic '' ...
, recommended lead (or lead-coated) vessels for the preparation of
sweeteners and preservatives added to wine and food. The lead conferred an agreeable taste due to the formation of "sugar of lead" (lead(II) acetate), whereas copper or
bronze
Bronze is an alloy consisting primarily of copper, commonly with about 12–12.5% tin and often with the addition of other metals (including aluminium, manganese, nickel, or zinc) and sometimes non-metals, such as phosphorus, or metalloids such ...
vessels could impart a bitter flavor through
verdigris
Verdigris is the common name for blue-green, copper-based pigments that form a patina on copper, bronze, and brass. The technical literature is ambiguous as to its chemical composition. Some sources refer to "neutral verdigris" as copper(II) ac ...
formation.
The Roman author
Vitruvius
Vitruvius (; c. 80–70 BC – after c. 15 BC) was a Roman architect and engineer during the 1st century BC, known for his multi-volume work entitled ''De architectura''. He originated the idea that all buildings should have three attribute ...
reported the health dangers of lead and modern writers have suggested that lead poisoning played a major role in the decline of the Roman Empire. Other researchers have criticized such claims, pointing out, for instance, that not all abdominal pain is caused by lead poisoning. According to archaeological research, Roman
lead pipe
A pipe is a tubular section or hollow cylinder, usually but not necessarily of circular cross-section, used mainly to convey substances which can flow — liquids and gases (fluids), slurries, powders and masses of small solids. It ...
s increased lead levels in tap water but such an effect was "unlikely to have been truly harmful". When lead poisoning did occur, victims were called "saturnine", dark and cynical, after the ghoulish father of the gods,
Saturn
Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine and a half times that of Earth. It has only one-eighth the average density of Earth; h ...
. By association, lead was considered the father of all metals. Its status in Roman society was low as it was readily available and cheap.
Confusion with tin and antimony
Since the
Bronze Age
The Bronze Age is a historic period, lasting approximately from 3300 BC to 1200 BC, characterized by the use of bronze, the presence of writing in some areas, and other early features of urban civilization. The Bronze Age is the second pri ...
metallurgists and engineers have understood the difference between rare and valuable
tin
Tin is a chemical element with the symbol Sn (from la, stannum) and atomic number 50. Tin is a silvery-coloured metal.
Tin is soft enough to be cut with little force and a bar of tin can be bent by hand with little effort. When bent, t ...
, essential for alloying with copper to produce tough and corrosion resistant
bronze
Bronze is an alloy consisting primarily of copper, commonly with about 12–12.5% tin and often with the addition of other metals (including aluminium, manganese, nickel, or zinc) and sometimes non-metals, such as phosphorus, or metalloids such ...
, and ‘cheap and cheerful’ lead. However the nomenclature in some languages is similar. Romans called lead ("black lead"), and tin ("bright lead"). The association of lead and tin can be seen in other languages: the word in
Czech
Czech may refer to:
* Anything from or related to the Czech Republic, a country in Europe
** Czech language
** Czechs, the people of the area
** Czech culture
** Czech cuisine
* One of three mythical brothers, Lech, Czech, and Rus'
Places
*Czech, ...
translates to "lead", but in Russian, its
cognate
In historical linguistics, cognates or lexical cognates are sets of words in different languages that have been inherited in direct descent from an etymology, etymological ancestor in a proto-language, common parent language. Because language c ...
() means "tin". To add to the confusion, lead bore a close relation to antimony: both elements commonly occur as sulfides (galena and
stibnite
Stibnite, sometimes called antimonite, is a sulfide mineral with the formula Sb2 S3. This soft grey material crystallizes in an orthorhombic space group. It is the most important source for the metalloid antimony. The name is derived from the ...
), often together. Pliny incorrectly wrote that stibnite would give lead on heating, instead of antimony. In countries such as Turkey and India, the originally Persian name came to refer to either antimony sulfide or lead sulfide, and in some languages, such as Russian, gave its name to antimony ().
Middle Ages and the Renaissance
Lead mining in Western Europe declined after the fall of the
Western Roman Empire
The Western Roman Empire comprised the western provinces of the Roman Empire at any time during which they were administered by a separate independent Imperial court; in particular, this term is used in historiography to describe the period fr ...
, with
Arabian Iberia being the only region having a significant output. The largest production of lead occurred in South and East Asia, especially China and India, where lead mining grew rapidly.
In Europe, lead production began to increase in the 11th and 12th centuries, when it was again used for roofing and piping. Starting in the 13th century, lead was used to create
stained glass
Stained glass is coloured glass as a material or works created from it. Throughout its thousand-year history, the term has been applied almost exclusively to the windows of churches and other significant religious buildings. Although tradition ...
. In the
European
European, or Europeans, or Europeneans, may refer to:
In general
* ''European'', an adjective referring to something of, from, or related to Europe
** Ethnic groups in Europe
** Demographics of Europe
** European cuisine, the cuisines of Europe ...
and
Arabian
The Arabian Peninsula, (; ar, شِبْهُ الْجَزِيرَةِ الْعَرَبِيَّة, , "Arabian Peninsula" or , , "Island of the Arabs") or Arabia, is a peninsula of Western Asia, situated northeast of Africa on the Arabian Plate. ...
traditions of
alchemy
Alchemy (from Arabic: ''al-kīmiyā''; from Ancient Greek: χυμεία, ''khumeía'') is an ancient branch of natural philosophy, a philosophical and protoscientific tradition that was historically practiced in China, India, the Muslim world, ...
, lead (symbol ♄ in the European tradition) was considered an impure
base metal
A base metal is a common and inexpensive metal, as opposed to a precious metal such as gold or silver. In numismatics, coins often derived their value from the precious metal content; however, base metals have also been used in coins in the past ...
which, by the separation, purification and balancing of its constituent essences, could be transformed to pure and incorruptible gold. During the period, lead was used increasingly for
adulterating wine. The use of such wine was forbidden for use in Christian rites by a
papal bull in 1498, but it continued to be imbibed and resulted in mass poisonings up to the late 18th century. Lead was a key material in parts of the
printing press
A printing press is a mechanical device for applying pressure to an inked surface resting upon a printing, print medium (such as paper or cloth), thereby transferring the ink. It marked a dramatic improvement on earlier printing methods in wh ...
, and lead dust was commonly inhaled by print workers, causing lead poisoning. Lead also became the chief material for making bullets for firearms: it was cheap, less damaging to iron gun barrels, had a higher density (which allowed for better retention of velocity), and its lower melting point made the production of bullets easier as they could be made using a wood fire. Lead, in the form of
Venetian ceruse
Venetian ceruse, also known as ''blanc de ceruse de Venise'' and Spirits of Saturn, was a 16th-century cosmetic used as a skin whitener. It was in great demand and considered the best available at the time, supposedly containing the best quality ...
, was extensively used in cosmetics by Western European aristocracy as whitened faces were regarded as a sign of modesty. This practice later expanded to white wigs and eyeliners, and only faded out with the
French Revolution
The French Revolution ( ) was a period of radical political and societal change in France that began with the Estates General of 1789 and ended with the formation of the French Consulate in November 1799. Many of its ideas are considere ...
in the late 18th century. A similar fashion appeared in Japan in the 18th century with the emergence of the
geisha
{{Culture of Japan, Traditions, Geisha
{{nihongo, Geisha, 芸者 ({{IPAc-en, ˈ, ɡ, eɪ, ʃ, ə; {{IPA-ja, ɡeːɕa, lang), also known as {{nihongo, , 芸子, geiko (in Kyoto and Kanazawa) or {{nihongo, , 芸妓, geigi, are a class of female ...
s, a practice that continued long into the 20th century. The white faces of women "came to represent their feminine virtue as Japanese women", with lead commonly used in the whitener.
Outside Europe and Asia
In the
New World
The term ''New World'' is often used to mean the majority of Earth's Western Hemisphere, specifically the Americas."America." ''The Oxford Companion to the English Language'' (). McArthur, Tom, ed., 1992. New York: Oxford University Press, p. 3 ...
, lead production was recorded soon after the arrival of European settlers. The earliest record dates to 1621 in the English
Colony of Virginia
The Colony of Virginia, chartered in 1606 and settled in 1607, was the first enduring English colonial empire, English colony in North America, following failed attempts at settlement on Newfoundland (island), Newfoundland by Sir Humphrey GilbertG ...
, fourteen years after its foundation. In Australia, the first mine opened by colonists on the continent was a lead mine, in 1841. In Africa, lead mining and smelting were known in the
Benue Trough
The Benue Trough is a major geological structure underlying a large part of Nigeria and extending about 1,000 km northeast from the Bight of Benin to Lake Chad. It is part of the broader West and Central African Rift System.
Location
The t ...
and the lower
Congo Basin
The Congo Basin (french: Bassin du Congo) is the sedimentary basin of the Congo River. The Congo Basin is located in Central Africa, in a region known as west equatorial Africa. The Congo Basin region is sometimes known simply as the Congo. It con ...
, where lead was used for trade with Europeans, and as a currency by the 17th century, well before the
scramble for Africa
The Scramble for Africa, also called the Partition of Africa, or Conquest of Africa, was the invasion, annexation, division, and colonisation of Africa, colonization of most of Africa by seven Western Europe, Western European powers during a ...
.
Industrial Revolution
![Lead mining Barber 1865p321cropped](https://upload.wikimedia.org/wikipedia/commons/5/52/Lead_mining_Barber_1865p321cropped.jpg)
In the second half of the 18th century, Britain, and later continental Europe and the United States, experienced the
Industrial Revolution
The Industrial Revolution was the transition to new manufacturing processes in Great Britain, continental Europe, and the United States, that occurred during the period from around 1760 to about 1820–1840. This transition included going f ...
. This was the first time during which lead production rates exceeded those of Rome. Britain was the leading producer, losing this status by the mid-19th century with the depletion of its mines and the development of lead mining in Germany, Spain, and the United States. By 1900, the United States was the leader in global lead production, and other non-European nations—Canada, Mexico, and Australia—had begun significant production; production outside Europe exceeded that within. A great share of the demand for lead came from plumbing and painting—
lead paint
Lead paint or lead-based paint is paint containing lead. As pigment, lead(II) chromate (, "chrome yellow"), lead(II,IV) oxide, (, "red lead"), and lead(II) carbonate (, "white lead") are the most common forms.. Lead is added to paint to acceler ...
s were in regular use. At this time, more (working class) people were exposed to the metal and lead poisoning cases escalated. This led to research into the effects of lead intake. Lead was proven to be more dangerous in its fume form than as a solid metal. Lead poisoning and
gout
Gout ( ) is a form of inflammatory arthritis characterized by recurrent attacks of a red, tender, hot and swollen joint, caused by deposition of monosodium urate monohydrate crystals. Pain typically comes on rapidly, reaching maximal intensit ...
were linked; British physician
Alfred Baring Garrod
Sir Alfred Baring Garrod (3 May 1819 – 28 December 1907) was an English physician.
Garrod was born in Ipswich, the son of Robert and Sarah (née Ennew) Garrod. He initially apprenticed at Ipswich Hospital, and later moved to University College ...
noted a third of his gout patients were plumbers and painters. The effects of chronic ingestion of lead, including mental disorders, were also studied in the 19th century. The first laws aimed at decreasing lead poisoning in factories were enacted during the 1870s and 1880s in the United Kingdom.
Modern era
![Dutch_boy_collier_white_lead](https://upload.wikimedia.org/wikipedia/commons/4/44/Dutch_boy_collier_white_lead.png)
Further evidence of the threat that lead posed to humans was discovered in the late 19th and early 20th centuries. Mechanisms of harm were better understood, lead blindness was documented, and the element was phased out of public use in the United States and Europe. The United Kingdom introduced mandatory factory inspections in 1878 and appointed the first Medical Inspector of Factories in 1898; as a result, a 25-fold decrease in lead poisoning incidents from 1900 to 1944 was reported. Most European countries banned lead paint—commonly used because of its opacity and water resistance—for interiors by 1930.
The last major human exposure to lead was the addition of tetraethyllead to gasoline as an
antiknock agent
An antiknock agent is a gasoline additive used to reduce engine knocking and increase the fuel's octane rating by raising the temperature and pressure at which auto-ignition occurs. The mixture known as gasoline or petrol, when used in high compr ...
, a practice that originated in the United States in 1921. It was phased out in the United States and the
European Union
The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been des ...
by 2000.
In the 1970s, the United States and Western European countries introduced legislation to reduce lead air pollution. The impact was significant: while a study conducted by the
Centers for Disease Control and Prevention
The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services, and is headquartered in Atlanta, Georgi ...
in the United States in 1976–1980 showed that 77.8% of the population had elevated
blood lead level
Blood lead level (BLL), is a measure of the amount of lead in the blood. Lead is a toxic heavy metal and can cause neurological damage, especially among children, at any detectable level. High lead levels cause decreased vitamin D and haemoglob ...
s, in 1991–1994, a study by the same institute showed the share of people with such high levels dropped to 2.2%. The main product made of lead by the end of the 20th century was the
lead–acid battery
The lead–acid battery is a type of rechargeable battery first invented in 1859 by French physicist Gaston Planté. It is the first type of rechargeable battery ever created. Compared to modern rechargeable batteries, lead–acid batteries have ...
.
From 1960 to 1990, lead output in the
Western Bloc
The Western Bloc, also known as the Free Bloc, the Capitalist Bloc, the American Bloc, and the NATO Bloc, was a coalition of countries that were officially allied with the United States during the Cold War of 1947–1991. It was spearheaded by ...
grew by about 31%. The share of the world's lead production by the
Eastern Bloc
The Eastern Bloc, also known as the Communist Bloc and the Soviet Bloc, was the group of socialist states of Central and Eastern Europe, East Asia, Southeast Asia, Africa, and Latin America under the influence of the Soviet Union that existed du ...
increased from 10% to 30%, from 1950 to 1990, with the
Soviet Union
The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen national ...
being the world's largest producer during the mid-1970s and the 1980s, and China starting major lead production in the late 20th century. Unlike the European communist countries, China was largely unindustrialized by the mid-20th century; in 2004, China surpassed Australia as the largest producer of lead. As was the case during European industrialization, lead has had a negative effect on health in China.
Production
![Evolution production plomb](https://upload.wikimedia.org/wikipedia/commons/2/2e/Evolution_production_plomb.svg)
As of 2014, production of lead is increasing worldwide due to its use in lead–acid batteries. There are two major categories of production: primary from mined ores, and secondary from scrap. In 2014, 4.58 million metric tons came from primary production and 5.64 million from secondary production. The top three producers of mined lead concentrate in that year were China, Australia, and the United States. The top three producers of refined lead were China, the United States, and India. According to the
International Resource Panel
The International Resource Panel is a scientific panel of experts that aims to help nations use natural resources sustainably without compromising economic growth and human needs. It provides independent scientific assessments and expert advice on ...
's
Metal Stocks in Society report
The report Metal Stocks in Society: Scientific Synthesis was the first of six scientific assessments on global metals to be published by the International Resource Panel (IRP) of the United Nations Environment Programme. The IRP provides independ ...
of 2010, the total amount of lead in use, stockpiled, discarded, or dissipated into the environment, on a global basis, is 8 kg per capita. Much of this is in more developed countries (20–150 kg per capita) rather than less developed ones (1–4 kg per capita).
The primary and secondary lead production processes are similar. Some primary production plants now supplement their operations with scrap lead, and this trend is likely to increase in the future. Given adequate techniques, lead obtained via secondary processes is indistinguishable from lead obtained via primary processes. Scrap lead from the building trade is usually fairly clean and is re-melted without the need for smelting, though refining is sometimes needed. Secondary lead production is therefore cheaper, in terms of energy requirements, than is primary production, often by 50% or more.
Primary
Most lead ores contain a low percentage of lead (rich ores have a typical content of 3–8%) which must be concentrated for extraction. During initial processing, ores typically undergo crushing,
dense-medium separation,
grinding
Grind is the cross-sectional shape of a blade.
Grind, grinds, or grinding may also refer to:
Grinding action
* Grinding (abrasive cutting), a method of crafting
* Grinding (dance), suggestive club dancing
* Grinding (video gaming), repetitive and ...
,
froth flotation
Froth flotation is a process for selectively separating hydrophobic materials from hydrophilic. This is used in mineral processing, paper recycling and waste-water treatment industries. Historically this was first used in the mining industry, wher ...
, and drying. The resulting concentrate, which has a lead content of 30–80% by mass (regularly 50–60%), is then turned into (impure) lead metal.
There are two main ways of doing this: a two-stage process involving roasting followed by blast furnace extraction, carried out in separate vessels; or a direct process in which the extraction of the concentrate occurs in a single vessel. The latter has become the most common route, though the former is still significant.
roasted
Roasting is a cooking method that uses dry heat where hot air covers the food, cooking it evenly on all sides with temperatures of at least from an open flame, oven, or other heat source. Roasting can enhance the flavor through caramelization ...
in air to oxidize the lead sulfide:
: 2 PbS(s) + 3 O
2(g) → 2 PbO(s) + 2 SO
2(g)↑
As the original concentrate was not pure lead sulfide, roasting yields not only the desired lead(II) oxide, but a mixture of oxides, sulfates, and silicates of lead and of the other metals contained in the ore. This impure lead oxide is reduced in a
coke-fired blast furnace to the (again, impure) metal:
: 2 PbO(s) + C(s) → 2 Pb(s) + CO
2(g)↑
Impurities are mostly arsenic, antimony, bismuth, zinc, copper, silver, and gold. Typically they are removed in a series of
pyrometallurgical processes. The melt is treated in a
reverberatory furnace
A reverberatory furnace is a metallurgical or process furnace that isolates the material being processed from contact with the fuel, but not from contact with combustion gases. The term ''reverberation'' is used here in a generic sense of ''rebo ...
with air, steam, and sulfur, which oxidizes the impurities except for silver, gold, and bismuth. Oxidized contaminants float to the
top of the melt and are skimmed off. Metallic silver and gold are removed and recovered economically by means of the
Parkes process
The Parkes process is a pyrometallurgical industrial process for removing silver
Silver is a chemical element with the Symbol (chemistry), symbol Ag (from the Latin ', derived from the Proto-Indo-European wikt:Reconstruction:Proto-Indo-Europ ...
, in which zinc is added to lead. Zinc, which is immiscible in lead, dissolves the silver and gold. The zinc solution can be separated from the lead, and the silver and gold retrieved. De-silvered lead is freed of bismuth by the
Betterton–Kroll process
The Betterton-Kroll Process is a pyrometallurgical process for refining lead from lead bullion(lead that still contains significant amounts of impurities). Developed by William Justin Kroll in 1922, the Betterton–Kroll process is one of the fin ...
, treating it with metallic calcium and
magnesium
Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...
. The resulting bismuth dross can be skimmed off.
Alternatively to the pyrometallurgical processes, very pure lead can be obtained by processing smelted lead electrolytically using the
Betts process. Anodes of impure lead and cathodes of pure lead are placed in an electrolyte of lead
fluorosilicate
Hexafluorosilicic acid is an inorganic compound with the chemical formula . Aqueous solutions of hexafluorosilicic acid consist of salts of the cation and hexafluorosilicate anion. These salts and their aqueous solutions are colorless.
Hexaflu ...
(PbSiF
6). Once electrical potential is applied, impure lead at the anode dissolves and plates onto the cathode, leaving the majority of the impurities in solution. This is a high-cost process and thus mostly reserved for refining bullion containing high percentages of impurities.
Direct process
In this process, lead bullion and
slag
Slag is a by-product of smelting (pyrometallurgical) ores and used metals. Broadly, it can be classified as ferrous (by-products of processing iron and steel), ferroalloy (by-product of ferroalloy production) or non-ferrous/base metals (by-prod ...
is obtained directly from lead concentrates. The lead sulfide concentrate is melted in a furnace and oxidized, forming lead monoxide. Carbon (as coke or
coal gas
Coal gas is a flammable gaseous fuel made from coal and supplied to the user via a piped distribution system. It is produced when coal is heated strongly in the absence of air. Town gas is a more general term referring to manufactured gaseous ...
) is added to the molten charge along with flux (metallurgy), fluxing agents. The lead monoxide is thereby reduced to metallic lead, in the midst of a slag rich in lead monoxide.
If the input is rich in lead, as much as 80% of the original lead can be obtained as bullion; the remaining 20% forms a slag rich in lead monoxide. For a low-grade feed, all of the lead can be oxidized to a high-lead slag. Metallic lead is further obtained from the high-lead (25–40%) slags via submerged fuel combustion or injection, reduction assisted by an electric furnace, or a combination of both.
Alternatives
Research on a cleaner, less energy-intensive lead extraction process continues; a major drawback is that either too much lead is lost as waste, or the alternatives result in a high sulfur content in the resulting lead metal. Hydrometallurgy, Hydrometallurgical extraction, in which anodes of impure lead are immersed into an electrolyte and pure lead is deposited (Electrowinning, electrowound) onto a cathode, is a technique that may have potential, but is not currently economical except in cases where electricity is very cheap.
Secondary
Smelting, which is an essential part of the primary production, is often skipped during secondary production. It is only performed when metallic lead has undergone significant oxidation. The process is similar to that of primary production in either a blast furnace or a rotary furnace, with the essential difference being the greater variability of yields: blast furnaces produce hard lead (10% antimony) while reverberatory and rotary kiln furnaces produced semisoft lead (3–4% antimony).
The ISASMELT process is a more recent smelting method that may act as an extension to primary production; battery paste from spent lead–acid batteries (containing lead sulfate and lead oxides) has its sulfate removed by treating it with alkali, and is then treated in a coal-fueled furnace in the presence of oxygen, which yields impure lead, with antimony the most common impurity. Refining of secondary lead is similar to that of primary lead; some refining processes may be skipped depending on the material recycled and its potential contamination.
Of the sources of lead for recycling, lead–acid batteries are the most important; lead pipe, sheet, and cable sheathing are also significant.
Applications
![Lead shielding](https://upload.wikimedia.org/wikipedia/commons/2/2b/Lead_shielding.jpg)
Contrary to popular belief, pencil leads in wooden pencils have never been made from lead. When the pencil originated as a wrapped graphite writing tool, the particular type of graphite used was named Plumbago (mineral)#Plumbago, ''plumbago'' (literally, ''act for lead'' or ''lead mockup'').
Elemental form
Lead metal has several useful mechanical properties, including high density, low melting point, ductility, and relative inertness. Many metals are superior to lead in some of these aspects but are generally less common and more difficult to extract from parent ores. Lead's toxicity has led to its phasing out for some uses.
Lead has been used for bullets since their invention in the Middle Ages. It is inexpensive; its low melting point means small arms ammunition and shotgun pellets can be cast with minimal technical equipment; and it is denser than other common metals, which allows for better retention of velocity. It remains the main material for bullets, alloyed with other metals as hardeners. Concerns have been raised that lead bullets used for hunting can damage the environment.
Lead's high density and resistance to corrosion have been exploited in a number of related applications. It is used as ballast in sailboat keels; its density allows it to take up a small volume and minimize water resistance, thus counterbalancing the heeling effect of wind on the sails. It is used in scuba diving diving weighting system, weight belts to counteract the diver's buoyancy. In 1993, the base of the Leaning Tower of Pisa was stabilized with 600 tonnes of lead. Because of its corrosion resistance, lead is used as a protective sheath for underwater cables.
Lead has many uses in the construction industry; lead sheets are used as architectural metals in roofing material, Cladding (construction), cladding, Flashing (weatherproofing), flashing, rain gutter, gutters and gutter joints, and on roof parapets. Lead is still used in statues and sculptures, including for armature (sculpture), armatures. In the past it was often used to tire balance, balance the wheels of cars; for environmental reasons this use is being phased out in favor of other materials.
Lead is added to copper alloys, such as brass and bronze, to improve machinability and for its lubricant, lubricating qualities. Being practically insoluble in copper the lead forms solid globules in imperfections throughout the alloy, such as grain boundaries. In low concentrations, as well as acting as a lubricant, the globules hinder the formation of swarf as the alloy is worked, thereby improving machinability. Copper alloys with larger concentrations of lead are used in Bearing (mechanical), bearings. The lead provides lubrication, and the copper provides the load-bearing support.
Lead's high density, atomic number, and formability form the basis for use of lead as a barrier that absorbs sound, vibration, and radiation. Lead has no natural resonance frequencies; as a result, sheet-lead is used as a sound deadening layer in the walls, floors, and ceilings of sound studios. Organ pipes are often made from a lead alloy, mixed with various amounts of tin to control the tone of each pipe. Lead is an established lead shielding, shielding material from ionizing radiation, radiation in nuclear science and in X-ray rooms due to its denseness and high attenuation coefficient. Molten lead has been used as a coolant for lead-cooled fast reactors.
Batteries
The largest use of lead in the early 21st century is in Lead–acid battery, lead–acid batteries. The lead in batteries undergoes no direct contact with humans, so there are fewer toxicity concerns. People who work in lead battery production plants may be exposed to lead dust and inhale it. The reactions in the battery between lead, lead dioxide, and sulfuric acid provide a reliable source of voltage. Supercapacitors incorporating lead–acid batteries have been installed in kilowatt and megawatt scale applications in Australia, Japan, and the United States in frequency regulation, solar smoothing and shifting, wind smoothing, and other applications. These batteries have lower energy density and charge-discharge efficiency than lithium-ion battery, lithium-ion batteries, but are significantly cheaper.
Coating for cables
Lead is used in high voltage power cables as shell material to prevent water diffusion into insulation; this use is decreasing as lead is being phased out. Its use in
solder
Solder (; NA: ) is a fusible metal alloy used to create a permanent bond between metal workpieces. Solder is melted in order to wet the parts of the joint, where it adheres to and connects the pieces after cooling. Metals or alloys suitable ...
for electronics is also being phased out by some countries to reduce the amount of environmental hazard, environmentally hazardous waste. Lead is one of three metals used in the Oddy test for museum materials, helping detect organic acids, aldehydes, and acidic gases.
Compounds
![PbCrO4 and PbCrO4•PbO](https://upload.wikimedia.org/wikipedia/commons/3/3c/PbCrO4_and_PbCrO4%E2%80%A2PbO.jpg)
In addition to being the main application for lead metal, lead-acid batteries are also the main consumer of lead compounds. The energy storage/release reaction used in these devices involves lead sulfate and lead dioxide:
:(s) + (s) + 2(aq) → 2(s) + 2(l)
Other applications of lead compounds are very specialized and often fading. Lead-based coloring agents are used in ceramic glazes and glass, especially for red and yellow shades. While lead paints are phased out in Europe and North America, they remain in use in less developed countries such as China, India, or Indonesia. Lead tetraacetate and lead dioxide are used as oxidizing agents in organic chemistry. Lead is frequently used in the polyvinyl chloride coating of electrical cords. It can be used to treat candle wicks to ensure a longer, more even burn. Because of its toxicity, European and North American manufacturers use alternatives such as zinc. Lead glass is composed of 12–28% Lead(II) oxide, lead oxide, changing its optical characteristics and reducing the transmission of ionizing radiation, a property used in old TVs and computer monitors with cathode-ray tubes. Lead-based
semiconductor
A semiconductor is a material which has an electrical resistivity and conductivity, electrical conductivity value falling between that of a electrical conductor, conductor, such as copper, and an insulator (electricity), insulator, such as glas ...
s such as lead telluride and lead selenide are used in photovoltaic cells and infrared detectors.
Biological effects
Lead has no confirmed biological role, and there is no confirmed safe level of lead exposure. A 2009 Canadian–American study concluded that even at levels that are considered to pose little to no risk, lead may cause "adverse mental health outcomes". Its prevalence in the human body—at an adult average of 120 mg—is nevertheless exceeded only by zinc (2500 mg) and iron (4000 mg) among the heavy metals. Lead Salt (chemistry), salts are very efficiently absorbed by the body. A small amount of lead (1%) is stored in bones; the rest is excreted in urine and feces within a few weeks of exposure. Only about a third of lead is excreted by a child. Continual exposure may result in the bioaccumulation of lead.
Toxicity
Lead is a highly poisonous metal (whether inhaled or swallowed), affecting almost every organ and system in the human body. At airborne levels of 100 mg/m
3, it is IDLH, immediately dangerous to life and health. Most ingested lead is absorbed into the bloodstream. The primary cause of its toxicity is its predilection for interfering with the proper functioning of enzymes. It does so by binding to the sulfhydryl groups found on many enzymes, or mimicking and displacing other metals which act as cofactor (biochemistry), cofactors in many enzymatic reactions. The essential metals that lead interacts with include calcium, iron, and zinc. High levels of calcium and iron tend to provide some protection from lead poisoning; low levels cause increased susceptibility.
Effects
Lead can cause severe damage to the brain and kidneys and, ultimately, death. By mimicking calcium, lead can cross the blood–brain barrier. It degrades the myelin sheaths of neurons, reduces their numbers, interferes with neurotransmitter, neurotransmission routes, and decreases neuronal growth. In the human body, lead inhibits porphobilinogen synthase and ferrochelatase, preventing both porphobilinogen formation and the incorporation of iron into protoporphyrin IX, the final step in heme synthesis. This causes ineffective heme synthesis and microcytic anemia.
![Symptoms of lead poisoning (raster)](https://upload.wikimedia.org/wikipedia/commons/0/0d/Symptoms_of_lead_poisoning_%28raster%29.png)
Symptoms of lead poisoning include nephropathy, colic-like abdominal pains, and possibly weakness in the fingers, wrists, or ankles. Small blood pressure increases, particularly in middle-aged and older people, may be apparent and can cause anemia. Several studies, mostly cross-sectional, found an association between increased lead exposure and decreased heart rate variability. In pregnant women, high levels of exposure to lead may cause miscarriage. Chronic, high-level exposure has been shown to reduce fertility in males.
In a child's developing brain, lead interferes with synapse formation in the cerebral cortex, neurochemical development (including that of neurotransmitters), and the organization of ion channels. Early childhood exposure has been linked with an increased risk of sleep disturbances and excessive daytime drowsiness in later childhood. High blood levels are associated with delayed puberty in girls. The rise and fall in exposure to airborne lead from the combustion of tetraethyl lead in gasoline during the 20th century has been linked with historical increases and Lead–crime hypothesis, decreases in crime levels.
Exposure sources
Lead exposure is a global issue since lead mining and smelting, and battery manufacturing, disposal, and Battery recycling#Lead.E2.80.93acid batteries, recycling, are common in many countries. Lead enters the body via inhalation, ingestion, or skin absorption. Almost all inhaled lead is absorbed into the body; for ingestion, the rate is 20–70%, with children absorbing a higher percentage than adults.
Poisoning typically results from ingestion of food or water contaminated with lead, and less commonly after accidental ingestion of contaminated soil, dust, or lead-based paint. Seawater products can contain lead if affected by nearby industrial waters. Fruit and vegetables can be contaminated by high levels of lead in the soils they were grown in. Soil can be contaminated through particulate accumulation from lead in pipes, lead paint, and residual emissions from leaded gasoline.
The use of lead for water pipes is plumbosolvency, a problem in areas with soft or acidic water. Hard water forms insoluble protective layers on the inner surface of the pipes, whereas soft and acidic water dissolves the lead pipes. Dissolved carbon dioxide in the carried water may result in the formation of soluble lead bicarbonate; oxygenated water may similarly dissolve lead as lead(II) hydroxide. Drinking such water, over time, can cause health problems due to the toxicity of the dissolved lead. The hard water, harder the water the more calcium bicarbonate and calcium sulfate, sulfate it will contain, and the more the inside of the pipes will be coated with a protective layer of lead carbonate or lead sulfate.
![Kymographic recording of the effect of lead on frog heart](https://upload.wikimedia.org/wikipedia/commons/b/be/Kymographic_recording_of_the_effect_of_lead_on_frog_heart..jpg)
Ingestion of applied lead-based paint is the major source of exposure for children:
a direct source is chewing on old painted window sills. Alternatively, as the applied dry paint deteriorates, it peels, is pulverized into dust and then enters the body through hand-to-mouth contact or contaminated food, water, or alcohol. Ingesting certain Traditional medicine#Home remedies, home remedies may result in exposure to lead or its compounds.
Inhalation is the second major exposure pathway, affecting smokers and especially workers in lead-related occupations. Cigarette smoke contains, among other toxic substances, radioactive lead-210. "As a result of EPA's regulatory efforts, levels of lead in the air [in the United States] decreased by 86 percent between 2010 and 2020."
The concentration of lead in the air in the United States fell below the national standard of 0.15 μg/m
3 in 2014.
Skin exposure may be significant for people working with organic lead compounds. The rate of skin absorption is lower for inorganic lead.
Lead in plastic toys
According to the United States Center for Disease Control, the use of lead in plastics has not been banned. Lead softens the plastic and makes it more flexible so that it can go back to its original shape. It may also be used in plastic toys to stabilize molecules from heat. Lead dust can be formed when plastic is exposed to sunlight, air, and detergents that break down the chemical bond between the lead and plastics.
Treatment
Treatment for lead poisoning normally involves the administration of dimercaprol and succimer. Acute cases may require the use of disodium calcium edetate, the calcium chelate, and the disodium salt of ethylenediaminetetraacetic acid (EDTA). It has a greater affinity for lead than calcium, with the result that lead chelate is formed by exchange and excreted in the urine, leaving behind harmless calcium.
Environmental effects
![Batteries at Thiaroye](https://upload.wikimedia.org/wikipedia/commons/0/08/Batteries_at_Thiaroye.jpg)
The extraction, production, use, and disposal of lead and its products have caused significant contamination of the Earth's soils and waters. Atmospheric emissions of lead were at their peak during the Industrial Revolution, and the leaded gasoline period in the second half of the twentieth century.
Lead releases originate from natural sources (i.e., concentration of the naturally occurring lead), industrial production, incineration and recycling, and mobilization of previously buried lead. In particular, as lead has been phased out from other uses, in the Global South, lead recycling operations designed to extract cheap lead used for global manufacturing have become a well documented source of exposure.
Elevated concentrations of lead persist in soils and sediments in post-industrial and urban areas; industrial emissions, including those arising from coal burning, continue in many parts of the world, particularly in the developing countries.
Lead can accumulate in soils, especially those with a high organic content, where it remains for hundreds to thousands of years. Environmental lead can compete with other metals found in and on plants surfaces potentially inhibiting photosynthesis and at high enough concentrations, negatively affecting plant growth and survival. Contamination of soils and plants can allow lead to ascend the food chain affecting microorganisms and animals. In animals, lead exhibits toxicity in many organs, damaging the nervous, kidney, renal, reproductive, hematopoiesis, hematopoietic, and cardiovascular systems after ingestion, inhalation, or skin absorption. Fish uptake lead from both water and sediment; bioaccumulation in the food chain poses a hazard to fish, birds, and sea mammals.
Anthropogenic lead includes lead from Shot (pellet), shot and Fishing sinker, sinkers. These are among the most potent sources of lead contamination along with lead production sites. Lead was banned for shot and sinkers in the United States in 2017, although that ban was only effective for a month, and a similar ban is being considered in the European Union.
Analytical methods for the determination of lead in the environment include spectrophotometry, X-ray fluorescence, atomic spectroscopy and electrochemistry, electrochemical methods. A specific ion-selective electrode has been developed based on the ionophore S,S'-methylenebis (N,N-diisobutyldithiocarbamate). An important biomarker assay for lead poisoning is δ-aminolevulinic acid levels in plasma, serum, and urine.
Restriction and remediation
![1plombs chasse cygne condé2](https://upload.wikimedia.org/wikipedia/commons/e/ef/1plombs_chasse_cygne_cond%C3%A92.jpg)
By the mid-1980s, there was significant decline in the use of lead in industry. In the United States, environmental regulations reduced or eliminated the use of lead in non-battery products, including gasoline, paints, solders, and water systems. Particulate control devices were installed in coal-fired power plants to capture lead emissions. In 1992, U.S. Congress required the Environmental Protection Agency to reduce the blood lead levels of the country's children. Lead use was further curtailed by the European Union's 2003 Restriction of Hazardous Substances Directive. A large drop in lead deposition occurred in the Netherlands after the 1993 national ban on use of lead shot for hunting and sport shooting: from 230 tonnes in 1990 to 47.5 tonnes in 1995.
In the United States, the permissible exposure limit for lead in the workplace, comprising metallic lead, inorganic lead compounds, and lead soaps, was set at 50 μg/m
3 over an 8-hour workday, and the
blood lead level
Blood lead level (BLL), is a measure of the amount of lead in the blood. Lead is a toxic heavy metal and can cause neurological damage, especially among children, at any detectable level. High lead levels cause decreased vitamin D and haemoglob ...
limit at 5 μg per 100 g of blood in 2012. Lead may still be found in harmful quantities in stoneware, Vinyl group, vinyl (such as that used for tubing and the insulation of electrical cords), and Chinese brass. Old houses may still contain lead paint. White lead paint has been White Lead (Painting) Convention, 1921, withdrawn from sale in industrialized countries, but specialized uses of other pigments such as yellow lead chromate remain. Stripping old paint by sanding produces dust which can be inhaled. Lead abatement programs have been mandated by some authorities in properties where young children live.
Lead waste, depending on the jurisdiction and the nature of the waste, may be treated as household waste (to facilitate lead abatement activities), or potentially hazardous waste requiring specialized treatment or storage. Lead is released into the environment in shooting places and a number of lead management practices have been developed to counter the lead contamination. Lead migration can be enhanced in acidic soils; to counter that, it is advised soils be treated with lime to neutralize the soils and prevent leaching of lead.
Research has been conducted on how to remove lead from biosystems by biological means: Fish bones are being researched for their ability to bioremediation, bioremediate lead in contaminated soil. The fungus ''Aspergillus versicolor'' is effective at absorbing lead ions from industrial waste before being released to water bodies. Several bacteria have been researched for their ability to remove lead from the environment, including the sulfate-reducing bacteria ''Desulfovibrio'' and ''Desulfotomaculum'', both of which are highly effective in aqueous solutions.
See also
* Derek Bryce-Smith, Derek Bryce-Smith – one of the earliest campaigners against lead in petrol in the UK
* Thomas Midgley Jr. – discovered that the addition of
tetraethyllead
Tetraethyllead (commonly styled tetraethyl lead), abbreviated TEL, is an organolead compound with the formula Pb( C2H5)4. It is a fuel additive, first being mixed with gasoline beginning in the 1920s as a patented octane rating booster that al ...
to gasoline prevented Engine knocking, "knocking" in internal combustion engines
* Clair Patterson – instrumental in the banning of tetraethyllead in gasoline in the US and lead solder in food cans.
* Robert A. Kehoe – foremost medical advocate for the use of tetraethyllead as an additive in gasoline.
Notes
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Further reading
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Table of contents*
External links
The Toxicology of Heavy Metals: Getting the Lead Out American Society for Clinical Pathology
{{Authority control
Lead,
Chemical elements
Post-transition metals
Native element minerals
Superconductors
Endocrine disruptors
IARC Group 2B carcinogens
Nuclear reactor coolants
Chemical elements with face-centered cubic structure