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A metal (from
Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 million as of ...
μέταλλον ''métallon'', "mine, quarry, metal") is a
material Material is a substance Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance, a material with a definite chemical composition * Matter, anything that has mass and t ...

material
that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts
electricity Electricity is the set of physical Physical may refer to: *Physical examination, a regular overall check-up with a doctor *Physical (album), ''Physical'' (album), a 1981 album by Olivia Newton-John **Physical (Olivia Newton-John song), "Physi ...
and
heat In thermodynamics Thermodynamics is a branch of physics that deals with heat, Work (thermodynamics), work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these ...

heat
relatively well. Metals are typically
malleable Ductility is a mechanical property commonly described as a material's amenability to drawing Drawing is a form of visual art in which an artist uses instruments to mark paper Paper is a thin sheet material produced by mechanically a ...
(they can be hammered into thin sheets) or
ductile Ductility is a mechanical property commonly described as a material's amenability to drawing Drawing is a form of visual art in which an artist uses instruments to mark paper Paper is a thin sheet material produced by mechanically a ...
(can be drawn into wires). A metal may be a
chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical elements cannot be broken down into simp ...
such as
iron Iron () is a with Fe (from la, ) and 26. It is a that belongs to the and of the . It is, on , right in front of (32.1% and 30.1%, respectively), forming much of Earth's and . It is the fourth most common . In its metallic state, iron ...

iron
; an
alloy An alloy is an admixture of metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts Elec ...
such as
stainless steel Stainless steel is a group of that contain a minimum of approximately 11% , a composition that prevents the from ing and also provides heat-resistant properties.“Corrosion: Chemical process". ''Encyclopædia Britannica'', Chicago, IL: Encyc ...
; or a molecular compound such as polymeric sulfur nitride. In physics, a metal is generally regarded as any substance capable of conducting electricity at a temperature of
absolute zero Absolute zero is the lowest limit of the thermodynamic temperature Thermodynamic temperature is the measure of ''absolute temperature'' and is one of the principal parameters of thermodynamics. A thermodynamic temperature reading of zero deno ...
. Many elements and compounds that are not normally classified as metals become metallic under high pressures. For example, the nonmetal
iodine Iodine is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical ele ...

iodine
gradually becomes a metal at a pressure of between 40 and 170 thousand times
atmospheric pressure Atmospheric pressure, also known as barometric pressure (after the barometer A barometer is a scientific instrument that is used to measure air pressure in a certain environment. Pressure tendency can forecast short term changes in the weather. ...
. Equally, some materials regarded as metals can become nonmetals.
Sodium Sodium is a with the  Na (from Latin ''natrium'') and  11. It is a soft, silvery-white, highly reactive . Sodium is an , being in of the periodic table. Its only stable is 23Na. The free metal does not occur in nature, and must be ...

Sodium
, for example, becomes a nonmetal at pressure of just under two million times atmospheric pressure. In chemistry, two elements that would otherwise qualify (in physics) as brittle metals—
arsenic Arsenic is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same num ...

arsenic
and
antimony Antimony is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science t ...

antimony
—are commonly instead recognised as
metalloid A metalloid is a type of which has a preponderance of in between, or that are a mixture of, those of s and s. There is no standard definition of a metalloid and no complete agreement on which elements are metalloids. Despite the lack of specifi ...
s due to their chemistry (predominantly non-metallic for arsenic, and balanced between metallicity and nonmetallicity for antimony). Around 95 of the 118 elements in the
periodic table The periodic table, also known as the periodic table of (the) chemical elements, is a tabular display of the chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is ...

periodic table
are metals (or are likely to be such). The number is inexact as the boundaries between metals,
nonmetal In , a nonmetal is a that usually gains s when reacting with a , and which forms an acid if combined with and . Nonmetals display more variety in color and state than do metals. About half are colored or colorless gases whereas nearly all m ...
s, and
metalloid A metalloid is a type of which has a preponderance of in between, or that are a mixture of, those of s and s. There is no standard definition of a metalloid and no complete agreement on which elements are metalloids. Despite the lack of specifi ...
s fluctuate slightly due to a lack of universally accepted definitions of the categories involved. In
astrophysics Astrophysics is a science that employs the methods and principles of physics in the study of astronomical objects and phenomena. Among the subjects studied are the Sun, other stars, galaxy, galaxies, extrasolar planets, the interstellar medium and ...
the term "metal" is cast more widely to refer to all chemical elements in a star that are heavier than
helium Helium (from el, ἥλιος, helios Helios; Homeric Greek: ), Latinized as Helius; Hyperion and Phaethon are also the names of his father and son respectively. often given the epithets Hyperion ("the one above") and Phaethon ("the shining") ...

helium
, and not just traditional metals. In this sense the first four "metals" collecting in stellar cores through nucleosynthesis are
carbon Carbon (from la, carbo "coal") is a with the C and 6. It is lic and —making four s available to form s. It belongs to group 14 of the periodic table. Carbon makes up only about 0.025 percent of Earth's crust. Three occur naturally, ...

carbon
,
nitrogen Nitrogen is the chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

nitrogen
,
oxygen Oxygen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same ...

oxygen
, and
neon Neon is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that co ...

neon
, all of which are strictly non-metals in chemistry. A star
fuses
fuses
lighter atoms, mostly hydrogen and helium, into heavier atoms over its lifetime. Used in that sense, the
metallicity In astronomy, metallicity is the Abundance of the chemical elements, abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astron ...
of an astronomical object is the proportion of its matter made up of the heavier chemical elements. Metals, as chemical elements, comprise 25% of the Earth's crust and are present in many aspects of modern life. The strength and resilience of some metals has led to their frequent use in, for example, high-rise building and bridge
construction Construction is a general term meaning the and to form , , or ,"Construction" def. 1.a. 1.b. and 1.c. ''Oxford English Dictionary'' Second Edition on CD-ROM (v. 4.0) Oxford University Press 2009 and comes from ''constructio'' (from ''com-' ...

construction
, as well as most vehicles, many
home appliance A home appliance, also referred to as a domestic appliance, an electric appliance or a household appliance, is a machine which assists in household A household consists of one or several persons who live in the same dwelling and share meals. I ...
s, tools, pipes, and railroad tracks.
Precious metal Precious metals are rare, naturally occurring metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearan ...
s were historically used as
coin A coin is a small, flat, (usually, depending on the country or value) round piece of metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or f ...

coin
age, but in the modern era,
coinage metals The coinage metals comprise, at a minimum, those metallic chemical elements which have historically been used as components in alloys used to mint coins. The term is not perfectly defined, however, since a number of metals have been used to make ...
have extended to at least 23 of the chemical elements. The history of refined metals is thought to begin with the use of copper about 11,000 years ago. Gold, silver, iron (as meteoric iron), lead, and brass were likewise in use before the first known appearance of bronze in the 5th millennium BCE. Subsequent developments include the production of early forms of steel; the discovery of
sodium Sodium is a with the  Na (from Latin ''natrium'') and  11. It is a soft, silvery-white, highly reactive . Sodium is an , being in of the periodic table. Its only stable is 23Na. The free metal does not occur in nature, and must be ...

sodium
—the first
light metal A light metal is any metal A metal (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its popula ...
—in 1809; the rise of modern
alloy steel Alloy steel is steel Steel is an alloy An alloy is an admixture of metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, s ...
s; and, since the end of World War II, the development of more sophisticated alloys.


Properties


Form and structure

Metals are shiny and
lustrous Lustre (British English British English (BrE) is the standard dialect of the English language English is a West Germanic languages, West Germanic language first spoken in History of Anglo-Saxon England, early medieval England, which ...
, at least when freshly prepared, polished, or fractured. Sheets of metal thicker than a few micrometres appear opaque, but
gold leaf Gold leaf is gold Gold is a chemical element with the Symbol (chemistry), symbol Au (from la, aurum) and atomic number 79, making it one of the higher atomic number elements that occur naturally. In a pure form, it is a brightness, brigh ...

gold leaf
transmits green light. The solid or liquid state of metals largely originates in the capacity of the metal atoms involved to readily lose their outer shell electrons. Broadly, the forces holding an individual atom's outer shell electrons in place are weaker than the attractive forces on the same electrons arising from interactions between the atoms in the solid or liquid metal. The electrons involved become delocalised and the atomic structure of a metal can effectively be visualised as a collection of atoms embedded in a cloud of relatively mobile electrons. This type of interaction is called a
metallic bond Metallic bonding is a type of chemical bond A chemical bond is a lasting attraction between atoms, ions or molecules that enables the formation of chemical compounds. The bond may result from the Coulomb's law, electrostatic force of att ...
. The strength of metallic bonds for different elemental metals reaches a maximum around the center of the
transition metal In chemistry, the term transition metal (or transition element) has three possible definitions: * The IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations tha ...
series, as these elements have large numbers of delocalized electrons. Although most elemental metals have higher
densities The density (more precisely, the volumetric mass density; also known as specific mass), of a substance is its mass per unit volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter Rho (letter), rho), although the L ...

densities
than most
nonmetals
nonmetals
, there is a wide variation in their densities,
lithium Lithium (from el, λίθος, lithos, lit=stone) is a with the Li and  3. It is a soft, silvery-white . Under , it is the least dense metal and the least dense solid element. Like all alkali metals, lithium is highly and flammable, a ...

lithium
being the least dense (0.534 g/cm3) and
osmium Osmium (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximat ...

osmium
(22.59 g/cm3) the most dense. Magnesium, aluminum and titanium are
light metal A light metal is any metal A metal (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its popula ...
s of significant commercial importance. Their respective densities of 1.7, 2.7 and 4.5 g/cm3 can be compared to those of the older structural metals, like iron at 7.9 and copper at 8.9 g/cm3. An iron ball would thus weigh about as much as three aluminum balls of equal volume. Metals are typically malleable and ductile, deforming under stress without cleaving. The nondirectional nature of metallic bonding is thought to contribute significantly to the ductility of most metallic solids. In contrast, in an ionic compound like table salt, when the planes of an
ionic bond Ionic bonding is a type of chemical bond A chemical bond is a lasting attraction between atoms, ions or molecules that enables the formation of chemical compounds. The bond may result from the Coulomb's law, electrostatic force of attraction be ...
slide past one another, the resultant change in location shifts ions of the same charge into close proximity, resulting in the
cleavage Cleavage may refer to: Science * Cleavage (crystal), in mineralogy and materials science, a process of splitting a crystal * Cleavage (geology), the foliation perpendicular to stress as a result of ductile deformation * Cleavage (embryo), in embr ...
of the crystal. Such a shift is not observed in a
covalently bonded A covalent bond is a chemical bond A chemical bond is a lasting attraction between atoms, ions or molecules that enables the formation of chemical compounds. The bond may result from the Coulomb's law, electrostatic force of attraction bet ...
crystal, such as a diamond, where fracture and crystal fragmentation occurs. Reversible
elastic deformation In engineering Engineering is the use of scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The discipline of engineering encompasses a broad ran ...
in metals can be described by
Hooke's Law The balance wheel at the core of many mechanical clocks and watches depends on Hooke's law. Since the torque generated by the coiled spring is proportional to the angle turned by the wheel, its oscillations have a nearly constant period. Hooke ...
for restoring forces, where the stress is linearly proportional to the strain. Heat or forces larger than a metal's
elastic limit In materials science The interdisciplinary field of materials science, also commonly termed materials science and engineering, covers the design and discovery of new materials, particularly solids. The intellectual origins of materials scie ...
may cause a permanent (irreversible) deformation, known as
plastic deformation In engineering, deformation refers to the change in size or shape of an object. ''Displacements'' are the ''absolute'' change in position of a point on the object. Deflection (engineering) , Deflection is the relative change in external displace ...
or
plasticity Plasticity may refer to: Science * Plasticity (physics), in engineering and physics, the propensity of a solid material to undergo permanent deformation under load * Neuroplasticity, in neuroscience, how entire brain structures, and the brain its ...
. An applied force may be a
tensile In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion (physics), motion and behavior through Spa ...
(pulling) force, a
compressive In continuum mechanics, stress is a physical quantity that expresses the internal forces that neighbouring particles of a continuous material exert on each other, while deformation (mechanics)#Strain, strain is the measure of the deformation of ...
(pushing) force, or a
shear Shear may refer to: Textile production * Animal shearing, the collection of wool from various species **Sheep shearing Sheep shearing is the process by which the woollen fleece of a sheep Sheep (''Ovis aries'') are quadruped The zebr ...
,
bending In applied mechanics Applied mechanics is a branch of the physical science Physical science is a branch of natural science that studies non-living systems, in contrast to life science. It in turn has many branches, each referred to as a " ...

bending
or torsion (twisting) force. A temperature change may affect the movement or displacement of structural defects in the metal such as
grain boundaries of a polycrystalline A crystallite is a small or even microscopic crystal 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, for ...
, point vacancies, line and screw dislocations,
stacking fault In crystallography, a stacking fault is a planar defect that can occur in crystalline materials.Fine, Morris E. (1921). "Introduction to Chemical and Structural Defects in Crystalline Solids", in ''Treatise on Solid State Chemistry Volume 1'', Sp ...
s and
twins Twins are two offspring In biology, offspring are the young creation of living organisms, produced either by a Asexual reproduction, single organism or, in the case of sexual reproduction, two organisms. Collective offspring may be known as a ...
in both
crystalline A crystal or crystalline solid is a solid Solid is one of the four fundamental states of matter (the others being liquid, gas and plasma). The molecules in a solid are closely packed together and contain the least amount of kinet ...

crystalline
and non-crystalline metals. Internal
slip Slip or SLIP may refer to: Science and technology Biology * Slip (fish) Sole is a fish belonging to several families. Generally speaking, they are members of the family Soleidae, but, outside Europe, the name ''sole'' is also applied to vario ...
, creep, and
metal fatigue In materials science, fatigue is the initiation and propagation of cracks in a material due to cyclic loading. Once a fatigue crack has initiated, it grows a small amount with each loading cycle, typically producing striation (fatigue), striatio ...
may ensue. The atoms of metallic substances are typically arranged in one of three common
crystal structure In crystallography Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids (see crystal structure). The word "crystallography" is derived from the Greek language, Greek words ''crystallon'' "co ...

crystal structure
s, namely
body-centered cubic 200px, A network model of a primitive cubic system 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 cryst ...
(bcc),
face-centered cubic 200px, A network model of a primitive cubic system In crystallography Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids (see crystal structure). The word "crystallography" is derived fro ...

face-centered cubic
(fcc), and
hexagonal close-packed In geometry Geometry (from the grc, γεωμετρία; ' "earth", ' "measurement") is, with , one of the oldest branches of . It is concerned with properties of space that are related with distance, shape, size, and relative position of ...
(hcp). In bcc, each atom is positioned at the center of a cube of eight others. In fcc and hcp, each atom is surrounded by twelve others, but the stacking of the layers differs. Some metals adopt different structures depending on the temperature. File:Cubic-body-centered.svg, Body-centered cubic crystal structure, with a 2-atom unit cell, as found in e.g. chromium, iron, and tungsten
File:Cubic-face-centered.svg, Face-centered cubic crystal structure, with a 4-atom unit cell, as found in e.g. aluminum, copper, and gold File:Hexagonal close packed.svg, Hexagonal close-packed crystal structure, with a 6-atom unit cell, as found in e.g. titanium, cobalt, and zinc The
unit cell In geometry Geometry (from the grc, γεωμετρία; ''wikt:γῆ, geo-'' "earth", ''wikt:μέτρον, -metron'' "measurement") is, with arithmetic, one of the oldest branches of mathematics. It is concerned with properties of space t ...

unit cell
for each crystal structure is the smallest group of atoms which has the overall symmetry of the crystal, and from which the entire crystalline lattice can be built up by repetition in three dimensions. In the case of the body-centered cubic crystal structure shown above, the unit cell is made up of the central atom plus one-eight of each of the eight corner atoms.


Electrical and thermal

The electronic structure of metals means they are relatively good conductors of electricity. Electrons in matter can only have fixed rather than variable energy levels, and in a metal the energy levels of the electrons in its electron cloud, at least to some degree, correspond to the energy levels at which electrical conduction can occur. In a semiconductor like silicon or a nonmetal like sulfur there is an energy gap between the electrons in the substance and the energy level at which electrical conduction can occur. Consequently, semiconductors and nonmetals are relatively poor conductors. The elemental metals have electrical conductivity values of from 6.9 × 103 S/cm for
manganese Manganese is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical e ...

manganese
to 6.3 × 105 S/cm for
silver Silver is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical ele ...

silver
. In contrast, a
semiconducting A semiconductor material has an electrical conductivity Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that quantifies how strongly it resists electric curren ...
metalloid such as
boron Boron is a chemical element In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behav ...

boron
has an electrical conductivity 1.5 × 10−6 S/cm. With one exception, metallic elements reduce their electrical conductivity when heated.
Plutonium Plutonium is a radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material co ...

Plutonium
increases its electrical conductivity when heated in the temperature range of around −175 to +125 °C. Metals are relatively good
conductors of heat
conductors of heat
. The electrons in a metal's electron cloud are highly mobile and easily able to pass on heat-induced vibrational energy. The contribution of a metal's electrons to its heat capacity and thermal conductivity, and the electrical conductivity of the metal itself can be calculated from the
free electron model In solid-state physics, the free electron model is a simple model for the behaviour of charge carriers in a metallic solid. It was developed in 1927, principally by Arnold Sommerfeld, who combined the Classical physics, classical Drude model with ...
. However, this does not take into account the detailed structure of the metal's ion lattice. Taking into account the positive potential caused by the arrangement of the ion cores enables consideration of the
electronic band structure In solid-state physics Solid-state physics is the study of rigid matter, or solids, through methods such as quantum mechanics, crystallography, electromagnetism, and metallurgy. It is the largest branch of condensed matter physics. Solid-state ...
and
binding energy In physics and chemistry, binding energy is the smallest amount of energy required to remove a particle from a system of particles or to disassemble a system of particles into individual parts. In the former meaning the term is predominantly use ...

binding energy
of a metal. Various mathematical models are applicable, the simplest being the
nearly free electron model In solid-state physics Solid-state physics is the study of rigid matter, or solids, through methods such as quantum mechanics, crystallography, electromagnetism, and metallurgy. It is the largest branch of condensed matter physics. Solid-state ...
.


Chemical

Metals are usually inclined to form
cations An ion () is an atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are u ...

cations
through electron loss. Most will react with oxygen in the air to form
oxide An oxide () is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held together by che ...
s over various timescales (
potassium Potassium is a chemical element In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, b ...

potassium
burns in seconds while iron
rust Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous ferric oxides, hydrous iron(III) oxides (Fe2O3·nH2O) and iron(III) oxi ...

rust
s over years). Some others, like
palladium Palladium is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical elem ...

palladium
,
platinum Platinum is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical el ...

platinum
and
gold Gold is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical elemen ...

gold
, do not react with the atmosphere at all. The
oxide An oxide () is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held together by che ...
s of metals are generally
basic BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming language In computer science Computer science deals with the theoretical foundations of information, algorithms and the ar ...
, as opposed to those of
nonmetals
nonmetals
, which are
acid An acid is a or capable of donating a (hydrogen ion H+) (a ), or, alternatively, capable of forming a with an (a ). The first category of acids are the proton donors, or s. In the special case of , proton donors form the H3O+ and are ...
ic or neutral. Exceptions are largely oxides with very high
oxidation state The oxidation state, or oxidation number, is the hypothetical charge Charge or charged may refer to: Arts, entertainment, and media Films * ''Charge, Zero Emissions/Maximum Speed'', a 2011 documentary Music * Charge (David Ford album), ''Charge ...
s such as CrO3, Mn2O7, and OsO4, which have strictly acidic reactions.
Painting Painting is the practice of applying paint Paint is any pigmented liquid A liquid is a nearly incompressible In fluid mechanics Fluid mechanics is the branch of physics concerned with the mechanics Mechanics (Ancient ...

Painting
,
anodizing s have an anodized aluminium surface that has been dyed; they are made in many colours. Anodizing is an electrolyte, electrolytic Passivation (chemistry), passivation process used to increase the thickness of the natural oxide layer on the surface ...
or
plating Plating is a surface covering in which a metal is deposited on a conductive surface. Plating has been done for hundreds of years; it is also critical for modern technology. Plating is used to decorate objects, for corrosion inhibition, to improve ...

plating
metals are good ways to prevent their
corrosion Corrosion is a that converts a refined metal into a more chemically stable form such as , , or . It is the gradual destruction of materials (usually a ) by chemical and/or electrochemical reaction with their environment. is the field dedica ...

corrosion
. However, a more reactive metal in the
electrochemical series The data values of standard electrode potentials (''E''°) are given in the table below, in volt The volt (symbol: V) is the SI derived unit, derived unit for electric potential, electric potential difference (voltage), and electromotive forc ...
must be chosen for coating, especially when chipping of the coating is expected. Water and the two metals form an
electrochemical cell An electrochemical cell is a device capable of either generating electrical energy Electrical energy is energy derived as a result of movement of electrically charged particles. When used loosely, ''electrical energy'' refers to energy that ha ...
, and if the coating is less reactive than the underlying metal, the coating actually ''promotes'' corrosion.


Periodic table distribution

In chemistry, the elements which are usually considered to be metals under ordinary conditions are shown in yellow on the periodic table below. The remaining elements are either metalloids (B, Si, Ge, As, Sb, and Te being commonly recognised as such) or nonmetals. Astatine (At) is usually classified as either a nonmetal or a metalloid, but some predictions expect it to be a metal; as such, it has been left blank due to the inconclusive state of the experimental knowledge. The other elements shown as having unknown properties are likely to be metals, but there is some doubt for copernicium (Cn) and oganesson (Og).


Alloys

An alloy is a substance having metallic properties and which is composed of two or more elements at least one of which is a metal. An alloy may have a variable or fixed composition. For example, gold and silver form an alloy in which the proportions of gold or silver can be freely adjusted; titanium and silicon form an alloy Ti2Si in which the ratio of the two components is fixed (also known as an
intermetallic compound An intermetallic (also called an intermetallic compound, intermetallic alloy, ordered intermetallic alloy, and a long-range-ordered alloy) is a type of metallic alloy An alloy is an admixture of metal A metal (from Ancient Greek, Gree ...
). Most pure metals are either too soft, brittle or chemically reactive for practical use. Combining different ratios of metals as alloys modifies the properties of pure metals to produce desirable characteristics. The aim of making alloys is generally to make them less brittle, harder, resistant to corrosion, or have a more desirable color and luster. Of all the metallic alloys in use today, the alloys of
iron Iron () is a with Fe (from la, ) and 26. It is a that belongs to the and of the . It is, on , right in front of (32.1% and 30.1%, respectively), forming much of Earth's and . It is the fourth most common . In its metallic state, iron ...

iron
(
steel Steel is an alloy An alloy is an admixture of metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appe ...

steel
,
stainless steel Stainless steel is a group of that contain a minimum of approximately 11% , a composition that prevents the from ing and also provides heat-resistant properties.“Corrosion: Chemical process". ''Encyclopædia Britannica'', Chicago, IL: Encyc ...
,
cast iron Cast iron is a group of iron-carbon alloys with a carbon content more than 2%. Its usefulness derives from its relatively low melting temperature. The alloy constituents affect its colour when fractured: white cast iron has carbide impuritie ...
,
tool steel Tool steel is any of various carbon steel Carbon steel is a steel with carbon content from about 0.05 up to 3.8 per cent by weight. The definition of carbon steel from the American Iron and Steel Institute (AISI) states: * no minimum content ...
,
alloy steel Alloy steel is steel Steel is an alloy An alloy is an admixture of metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, s ...
) make up the largest proportion both by quantity and commercial value. Iron alloyed with various proportions of carbon gives low, mid and high carbon steels, with increasing carbon levels reducing ductility and toughness. The addition of
silicon Silicon is a chemical element with the Symbol (chemistry), symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a Tetravalence, tetravalent metalloid and semiconductor. It is a member ...

silicon
will produce cast irons, while the addition of
chromium Chromium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science tha ...

chromium
,
nickel Nickel is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical elem ...

nickel
and
molybdenum Molybdenum is a with the Mo and 42. The name is from ''molybdaenum'', which is based on ', meaning , since its ores were confused with lead ores. Molybdenum minerals have been known throughout history, but the element was discovered (in the ...

molybdenum
to carbon steels (more than 10%) results in stainless steels. Other significant metallic alloys are those of
aluminum Aluminium (aluminum in American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the United States The United States of America (USA), commonly known as the Uni ...

aluminum
,
titanium Titanium is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical ele ...

titanium
,
copper Copper is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical elem ...

copper
and
magnesium Magnesium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

magnesium
. Copper alloys have been known since prehistory—
bronze Bronze is an alloy An alloy is an admixture of metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appear ...

bronze
gave the
Bronze Age The Bronze Age is a prehistoric Periodization, period that was characterized by the use of bronze, in some areas proto-writing, and other early features of urban civilization. The Bronze Age is the second principal period of the Three-age sys ...
its name—and have many applications today, most importantly in electrical wiring. The alloys of the other three metals have been developed relatively recently; due to their chemical reactivity they require
electrolytic An electrolyte is a substance that produces an conductivity (electrolytic), electrically conducting solution when dissolved in a polar solvent, such as water. The dissolved electrolyte separates into cations and anions, which disperse uniformly thr ...

electrolytic
extraction processes. The alloys of aluminum, titanium and magnesium are valued for their high strength-to-weight ratios; magnesium can also provide
electromagnetic shielding In electrical engineering Electrical engineering is an engineering discipline concerned with the study, design, and application of equipment, devices, and systems which use electricity, electronics, and electromagnetism. It emerged as an ide ...
. These materials are ideal for situations where high strength-to-weight ratio is more important than material cost, such as in aerospace and some automotive applications. Alloys specially designed for highly demanding applications, such as
jet engine A jet engine is a type of reaction engine A reaction engine is an engine or motor that produces thrust Thrust is a described quantitatively by . When a system expels or in one direction, the accelerated mass will cause a force of ...

jet engine
s, may contain more than ten elements.


Categories

Metals can be categorised according to their physical or chemical properties. Categories described in the subsections below include
ferrous In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds composed of atoms, mo ...
and
non-ferrous In metallurgy Metallurgy is a domain of Materials science, materials science and engineering that studies the physical and chemical behavior of metallic Chemical element, elements, their Inter-metallic alloy, inter-metallic compounds, and their ...
metals; brittle metals and
refractory metal Refractory metals are a class of metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts Elec ...
s; white metals;
heavy Heavy may refer to: Measures * Heavy (aeronautics), a term used by pilots and air traffic controllers to refer to aircraft capable of 300,000 lbs or more takeoff weight * Heavy, a characterization of objects with substantial weight In scien ...
and
light Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that is visual perception, perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nan ...
metals; and
base Base or BASE may refer to: Brands and enterprises * Base (mobile telephony provider), a Belgian mobile telecommunications operator *Base CRM Base CRM (originally Future Simple or PipeJump) is an enterprise software company based in Mountain Vie ...
, noble, and precious metals. The ''Metallic elements'' table in this section categorises the elemental metals on the basis of their chemical properties into
alkali In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and the changes they undergo dur ...
and
alkaline earth The alkaline earth metals are six chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that al ...
metals; transition and post-transition metals; and
lanthanide The lanthanide () or lanthanoid () series of chemical elements comprises the 15 metallic chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an elem ...
s and
actinide The actinoid (IUPAC nomenclature The International Union of Pure and Applied Chemistry The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations that represents chemis ...
s. Other categories are possible, depending on the criteria for inclusion. For example, the ferromagnetic metals—those metals that are magnetic at room temperature—are iron, cobalt, and nickel.


Ferrous and non-ferrous metals

The term "ferrous" is derived from the Latin language, Latin word meaning "containing iron". This can include pure iron, such as wrought iron, or an alloy such as
steel Steel is an alloy An alloy is an admixture of metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appe ...

steel
. Ferrous metals are often magnetism, magnetic, but not exclusively. Non-ferrous metals—alloys—lack appreciable amounts of iron.


Brittle metal

While nearly all metals are malleable or ductile, a few—beryllium, chromium, manganese, gallium, and bismuth—are brittle. Arsenic, and antimony, if admitted as metals, are brittle. Low values of the ratio of bulk elastic modulus to shear modulus (Pugh's criterion) are indicative of intrinsic brittleness.


Refractory metal

In materials science, metallurgy, and engineering, a refractory metal is a metal that is extraordinarily resistant to heat and wear. Which metals belong to this category varies; the most common definition includes niobium, molybdenum, tantalum, tungsten, and rhenium. They all have melting points above 2000 °C, and a high hardness at room temperature. File:Niobium crystals and 1cm3 cube.jpg, Niobium crystals, and a 1 cm3 anodizing, anodized niobium cube for comparison File:Molybdenum crystaline fragment and 1cm3 cube.jpg, Molybdenum crystals, and a 1 cm3 molybdenum cube for comparison File:Tantalum single crystal and 1cm3 cube.jpg, Tantalum single crystal, some crystalline fragments, and a 1 cm3 tantalum cube for comparison File:Wolfram evaporated crystals and 1cm3 cube.jpg, Tungsten rods with evaporated crystals, partially oxidized with colorful tarnish, and a 1 cm3 tungsten cube for comparison File:Rhenium single crystal bar and 1cm3 cube.jpg, Rhenium single crystal, a remelted bar, and a 1 cm3 rhenium cube for comparison


White metal

A white metal is any of range of white-coloured metals (or their alloys) with relatively low melting points. Such metals include zinc, cadmium, tin, antimony (here counted as a metal), lead, and bismuth, some of which are quite toxic. In Britain, the fine art trade uses the term "white metal" in auction catalogues to describe foreign silver items which do not carry British Assay Office marks, but which are nonetheless understood to be silver and are priced accordingly.


Heavy and light metals

A heavy metal is any relatively dense metal or
metalloid A metalloid is a type of which has a preponderance of in between, or that are a mixture of, those of s and s. There is no standard definition of a metalloid and no complete agreement on which elements are metalloids. Despite the lack of specifi ...
. More specific definitions have been proposed, but none have obtained widespread acceptance. Some heavy metals have niche uses, or are notably toxic; some are essential in trace amounts. All other metals are light metals.


Base, noble and precious metals

In chemistry, the term ''base metal'' is used informally to refer to a metal that is easily oxidation, oxidized or corrosion, corroded, such as reacting easily with dilute hydrochloric acid (HCl) to form a metal chloride and hydrogen. Examples include iron,
nickel Nickel is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical elem ...

nickel
, lead and zinc. Copper is considered a base metal as it is oxidized relatively easily, although it does not react with HCl. The term noble metal is commonly used in opposition to ''base metal''. Noble metals are resistant to
corrosion Corrosion is a that converts a refined metal into a more chemically stable form such as , , or . It is the gradual destruction of materials (usually a ) by chemical and/or electrochemical reaction with their environment. is the field dedica ...

corrosion
or oxidation, unlike most base metals. They tend to be precious metals, often due to perceived rarity. Examples include gold, platinum, silver, rhodium, iridium and palladium. In alchemy and numismatics, the term base metal is contrasted with precious metal, that is, those of high economic value. A longtime goal of the alchemists was the transmutation of base metals into precious metals including such coinage metals as silver and gold. Most coins today are made of base metals with fiat currency, no intrinsic value, in the past, coins frequently derived their value primarily from their precious metal content. Chemically, the precious metals (like the noble metals) are less reactivity (chemistry), reactive than most elements, have high Lustre (mineralogy), luster and high electrical conductivity. Historically, precious metals were important as currency, but are now regarded mainly as investment and industrial commodity, commodities. Gold,
silver Silver is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical ele ...

silver
,
platinum Platinum is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical el ...

platinum
and
palladium Palladium is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical elem ...

palladium
each have an ISO 4217 currency code. The best-known precious metals are gold and silver. While both have industrial uses, they are better known for their uses in art, jewelry, and currency, coinage. Other precious metals include the platinum group metals: ruthenium, rhodium, palladium,
osmium Osmium (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximat ...

osmium
, iridium, and platinum, of which platinum is the most widely traded. The demand for precious metals is driven not only by their practical use, but also by their role as investments and a store of value. Palladium and platinum, as of fall 2018, were valued at about three quarters the price of gold. Silver is substantially less expensive than these metals, but is often traditionally considered a precious metal in light of its role in coinage and jewelry.


Valve metals

In electrochemistry, a valve metal is a metal which passes current in only one direction.


Lifecycle


Formation

:''This sub-section deals with the formation of periodic table elemental metals since these form the basis of metallic materials, as defined in this article.'' Metals up to the iron peak, vicinity of iron (in the periodic table) are largely made via stellar nucleosynthesis. In this process, lighter elements from hydrogen to
silicon Silicon is a chemical element with the Symbol (chemistry), symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a Tetravalence, tetravalent metalloid and semiconductor. It is a member ...

silicon
undergo successive nuclear fusion, fusion reactions inside stars, releasing light and heat and forming heavier elements with higher atomic numbers. Heavier metals are not usually formed this way since fusion reactions involving such nuclei would consume rather than release energy. Rather, they are largely synthesised (from elements with a lower atomic number) by neutron capture, with the two main modes of this repetitive capture being the s-process and the r-process. In the s-process ("s" stands for "slow"), singular captures are separated by years or decades, allowing the less stable nuclei to beta decay, while in the r-process ("rapid"), captures happen faster than nuclei can decay. Therefore, the s-process takes a more or less clear path: for example, stable cadmium-110 nuclei are successively bombarded by free neutrons inside a star until they form cadmium-115 nuclei which are unstable and decay to form indium-115 (which is nearly stable, with a half-life times the age of the universe). These nuclei capture neutrons and form indium-116, which is unstable, and decays to form tin-116, and so on. In contrast, there is no such path in the r-process. The s-process stops at bismuth due to the short half-lives of the next two elements, polonium and astatine, which decay to bismuth or lead. The r-process is so fast it can skip this zone of instability and go on to create heavier elements such as thorium and uranium. Metals condense in planets as a result of stellar evolution and destruction processes. Stars lose much of their mass when it is stellar mass loss, ejected late in their lifetimes, and sometimes thereafter as a result of a neutron star merger, thereby increasing the abundance of elements heavier than helium in the interstellar medium. When gravitational attraction causes this matter to coalesce and collapse nebular hypothesis, new stars and planets are formed.


Abundance and occurrence

The Earth's crust is made of approximately 25% of metals by weight, of which 80% are light metals such as sodium, magnesium, and aluminum. Nonmetals (~75%) make up the rest of the crust. Despite the overall scarcity of some heavier metals such as copper, they can become concentrated in economically extractable quantities as a result of mountain building, erosion, or other geological processes. Metals are primarily found as lithophiles (rock-loving) or chalcophiles (ore-loving). Lithophile metals are mainly the s-block elements, the more reactive of the d-block elements. and the f-block elements. They have a strong affinity for oxygen and mostly exist as relatively low density silicate minerals. Chalcophile metals are mainly the less reactive d-block elements, and the period 4–6 p-block metals. They are usually found in (insoluble) sulfide minerals. Being denser than the lithophiles, hence sinking lower into the crust at the time of its solidification, the chalcophiles tend to be less abundant than the lithophiles. On the other hand, gold is a siderophile, or iron-loving element. It does not readily form compounds with either oxygen or sulfur. At the time of the Earth's formation, and as the most noble (inert) of metals, gold sank into the core due to its tendency to form high-density metallic alloys. Consequently, it is a relatively rare metal. Some other (less) noble metals—molybdenum, rhenium, the platinum group metals (ruthenium, rhodium, palladium, osmium, iridium, and platinum), germanium, and tin—can be counted as siderophiles but only in terms of their primary occurrence in the Earth (core, mantle and crust), rather the crust. These metals otherwise occur in the crust, in small quantities, chiefly as chalcophiles (less so in their native form). The rotating fluid outer core of the Earth's interior, which is composed mostly of iron, is thought to be the source of Earth's protective magnetic field. The core lies above Earth's solid inner core and below its mantle. If it could be rearranged into a column having a footprint it would have a height of nearly 700 light years. The magnetic field shields the Earth from the charged particles of the solar wind, and cosmic rays that would otherwise strip away the upper atmosphere (including the ozone layer that limits the transmission of ultraviolet radiation).


Extraction

Metals are often extracted from the Earth by means of mining ores that are rich sources of the requisite elements, such as bauxite. Ore is located by prospecting techniques, followed by the exploration and examination of deposits. Mineral sources are generally divided into Surface mining, surface mines, which are mined by excavation using heavy equipment, and Underground mining (hard rock), subsurface mines. In some cases, the sale price of the metal/s involved make it economically feasible to mine lower concentration sources. Once the ore is mined, the metals must be Extractive metallurgy, extracted, usually by chemical or electrolytic reduction. Pyrometallurgy uses high temperatures to convert ore into raw metals, while hydrometallurgy employs aqueous chemistry for the same purpose. The methods used depend on the metal and their contaminants. When a metal ore is an ionic compound of that metal and a non-metal, the ore must usually be smelting, smelted—heated with a reducing agent—to extract the pure metal. Many common metals, such as iron, are smelted using
carbon Carbon (from la, carbo "coal") is a with the C and 6. It is lic and —making four s available to form s. It belongs to group 14 of the periodic table. Carbon makes up only about 0.025 percent of Earth's crust. Three occur naturally, ...

carbon
as a reducing agent. Some metals, such as aluminum and
sodium Sodium is a with the  Na (from Latin ''natrium'') and  11. It is a soft, silvery-white, highly reactive . Sodium is an , being in of the periodic table. Its only stable is 23Na. The free metal does not occur in nature, and must be ...

sodium
, have no commercially practical reducing agent, and are extracted using electrolysis instead. Sulfide ores are not reduced directly to the metal but are roasted in air to convert them to oxides.


Uses

Metals are present in nearly all aspects of modern life. Iron, a heavy metals, heavy metal, may be the most common as it accounts for 90% of all refined metals; aluminum, a
light metal A light metal is any metal A metal (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its popula ...
, is the next most commonly refined metal. Pure iron may be the cheapest metallic element of all at cost of about US$0.07 per gram. Its ores are widespread; it is easy to refining, refine; and the technology involved has been developed over hundreds of years. Cast iron is even cheaper, at a fraction of US$0.01 per gram, because there is no need for subsequent purification. Platinum, at a cost of about $27 per gram, may be the most ubiquitous given its very high melting point, resistance to corrosion, electrical conductivity, and durability. It is said to be found in, or used to produce, 20% of all consumer goods. Polonium is likely to be the most expensive metal, at a notional cost of about $100,000,000 per gram, due to its scarcity and micro-scale production. Some metals and metal alloys possess high structural strength per unit mass, making them useful materials for carrying large loads or resisting impact damage. Metal alloys can be engineered to have high resistance to shear, torque and deformation. However the same metal can also be vulnerable to fatigue damage through repeated use or from sudden stress failure when a load capacity is exceeded. The strength and resilience of metals has led to their frequent use in high-rise building and bridge construction, as well as most vehicles, many appliances, tools, pipes, and railroad tracks. Metals are good conductors, making them valuable in electrical appliances and for carrying an electric current over a distance with little energy lost. Electrical power grids rely on metal cables to distribute electricity. Home electrical systems, for the most part, are wired with copper wire for its good conducting properties. The thermal conductivity of metals is useful for containers to heat materials over a flame. Metals are also used for heat sinks to protect sensitive equipment from overheating. The high reflectivity of some metals enables their use in mirrors, including precision astronomical instruments, and adds to the aesthetics of metallic jewelry. Some metals have specialized uses; mercury is a liquid at room temperature and is used in switches to complete a circuit when it flows over the switch contacts. Radioactive metals such as uranium and plutonium are used in Nuclear reactor technology, nuclear power plants to produce energy via nuclear fission. Shape memory alloys are used for applications such as pipes, fasteners and vascular stents. Metals can be dopant, doped with foreign molecules—organic, inorganic, biological and polymers. This doping entails the metal with new properties that are induced by the guest molecules. Applications in catalysis, medicine, electrochemical cells, corrosion and more have been developed.


Recycling

Demand for metals is closely linked to economic growth given their use in infrastructure, construction, manufacturing, and consumer goods. During the 20th century, the variety of metals used in society grew rapidly. Today, the development of major nations, such as China and India, and technological advances, are fuelling ever more demand. The result is that mining activities are expanding, and more and more of the world's metal stocks are above ground in use, rather than below ground as unused reserves. An example is the in-use stock of
copper Copper is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical elem ...

copper
. Between 1932 and 1999, copper in use in the U.S. rose from 73 g to 238 g per person.''The Recycling Rates of Metals: A Status Report''
2010, International Resource Panel, United Nations Environment Programme
Metals are inherently recyclable, so in principle, can be used over and over again, minimizing these negative environmental impacts and saving energy. For example, 95% of the energy used to make aluminum from bauxite ore is saved by using recycled material. Globally, metal recycling is generally low. In 2010, the International Resource Panel, hosted by the United Nations Environment Programme published reports on metal stocks that exist within society and their recycling rates. The authors of the report observed that the metal stocks in society can serve as huge mines above ground. They warned that the recycling rates of some rare metals used in applications such as mobile phones, battery packs for hybrid cars and fuel cells are so low that unless future end-of-life recycling rates are dramatically stepped up these critical metals will become unavailable for use in modern technology.


Biological interactions

The role of metallic elements in the evolution of cell biochemistry has been reviewed, including a detailed section on the role of calcium in redox enzymes. One or more of the elements
iron Iron () is a with Fe (from la, ) and 26. It is a that belongs to the and of the . It is, on , right in front of (32.1% and 30.1%, respectively), forming much of Earth's and . It is the fourth most common . In its metallic state, iron ...

iron
, cobalt,
nickel Nickel is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical elem ...

nickel
,
copper Copper is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical elem ...

copper
and zinc are essential to all higher forms of life. Molybdenum is an essential component of vitamin B12. Compounds of all other transition elements and post-transition elements are toxic to a greater or lesser extent, with few exceptions such as certain compounds of
antimony Antimony is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science t ...

antimony
and tin. Potential sources of metal poisoning include mining, tailings, industrial wastes, agricultural runoff, chemical hazard, occupational exposure, Environmental impact of paint, paints and treated wood, treated timber.


History


Prehistory

Copper, which occurs in native form, may have been the first metal discovered given its distinctive appearance, heaviness, and malleability compared to other stones or pebbles. Gold, silver, and iron (as meteoric iron), and lead were likewise discovered in prehistory. Forms of brass, an alloy of copper and zinc made by concurrently smelting the ores of these metals, originate from this period (although pure zinc was not isolated until the 13th century). The malleability of the solid metals led to the first attempts to craft metal ornaments, tools, and weapons. Meteoric iron containing nickel was discovered from time to time and, in some respects this was superior to any industrial steel manufactured up to the 1880s when alloy steels become prominent. File:NatCopper.jpg, Native metal#Copper, Native copper File:Gold-crystals.jpg, Gold crystals File:Silver crystal.jpg, Crystalline silver File:Widmanstatten hand.jpg, A slice of meteoric iron File:Lead electrolytic and 1cm3 cube.jpg, alt=Three, dark broccoli shaped clumps of oxidised lead with grossly distended buds, and a cube of lead which has a dull silvery appearance.,
redox, Oxidised lead
nodules and 1 cm3 cube
File:Akan MHNT.AC.AF.29.jpg, A brass weight (35 g)


Antiquity

The discovery of
bronze Bronze is an alloy An alloy is an admixture of metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appear ...

bronze
(an alloy of copper with arsenic or tin) enabled people to create metal objects which were harder and more durable than previously possible. Bronze tools, weapons, armor, and building materials such as decorative tiles were harder and more durable than their stone and copper ("Chalcolithic") predecessors. Initially, bronze was made of copper and
arsenic Arsenic is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same num ...

arsenic
(forming arsenic bronze) by smelting naturally or artificially mixed ores of copper and arsenic. The earliest Artifact (archaeology), artifacts so far known come from the Iranian plateau in the 5th millennium BCE. It was only later that tin was used, becoming the major non-copper ingredient of bronze in the late 3rd millennium BCE. Pure tin itself was first isolated in 1800 BCE by Chinese and Japanese metalworkers. Mercury was known to ancient Chinese and Indians before 2000 BCE, and found in Egyptian tombs dating from 1500 BCE. The earliest known production of steel, an iron-carbon alloy, is seen in pieces of ironware excavated from an archaeological site in Anatolia (Kaman-Kalehöyük) and are nearly 4,000 years old, dating from 1800 BCE. From about 500 BCE sword-makers of Toledo, Spain, were making early forms of
alloy steel Alloy steel is steel Steel is an alloy An alloy is an admixture of metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, s ...
by adding a mineral called wolframite, which contained tungsten and manganese, to iron ore (and carbon). The resulting Toledo steel came to the attention of Rome when used by Hannibal in the Punic Wars. It soon became the basis for the weaponry of Roman legions; their swords were said to have been "so keen that there is no helmet which cannot be cut through by them." Metallurgy in pre-Columbian America, In pre-Columbian America, objects made of tumbaga, an alloy of copper and gold, started being produced in Panama and Costa Rica between 300 and 500 CE. Small metal sculptures were common and an extensive range of tumbaga (and gold) ornaments comprised the usual regalia of persons of high status. At around the same time indigenous Ecuadorians were combining gold with a naturally-occurring platinum alloy containing small amounts of palladium, rhodium, and iridium, to produce miniatures and masks composed of a white gold-platinum alloy. The metal workers involved heated gold with Grain (metal), grains of the platinum alloy until the gold melted at which point the platinum group metals became bound within the gold. After cooling, the resulting conglomeration was hammered and reheated repeatedly until it became as homogenous as if all of the metals concerned had been melted together (attaining the melting points of the platinum group metals concerned was beyond the technology of the day). File:Tin-2.jpg, A droplet of solidified molten tin File:Pouring liquid mercury bionerd.jpg, alt=A silvery molasses-like liquid being poured into a circular container with a height equivalent to a smaller coin on its edge,
Mercury (element), Mercury being
poured into a petri dish
File:25 litrai en électrum représentant un trépied delphien.jpg, Electrum, a natural alloy of silver and gold, was often used for making coins. Shown is the Roman god Apollo, and on the obverse, a Delphi tripod (circa 310–305 BCE). File:Passover Plate (4047010755).jpg, A plate made of pewter, an alloy of 85–99% tin and (usually) copper. Pewter was first used around the beginning of the Bronze Age in the Near East. File:Museo del Oro - Tolima pectoral.jpg, A pectoral (ornamental breastplate) made of tumbaga, an alloy of gold and copper


Middle Ages

Arabic and medieval Alchemy, alchemists believed that all metals and matter were composed of the principle of sulfur, the father of all metals and carrying the combustible property, and the principle of mercury, the mother of all metals and carrier of the liquidity, fusibility, and volatility properties. These principles were not necessarily the common substances sulfur and mercury (element), mercury found in most laboratories. This theory reinforced the belief that all metals were destined to become gold in the bowels of the earth through the proper combinations of heat, digestion, time, and elimination of contaminants, all of which could be developed and hastened through the knowledge and methods of alchemy. Arsenic, zinc, antimony, and bismuth became known, although these were at first called semimetals or bastard metals on account of their immalleability. All four may have been used incidentally in earlier times without recognising their nature. Albertus Magnus is believed to have been the first to isolate arsenic from a compound in 1250, by heating soap together with arsenic trisulfide. Metallic zinc, which is brittle if impure, was isolated in India by 1300 AD. The first description of a procedure for isolating antimony is in the 1540 book ''De la pirotechnia'' by Vannoccio Biringuccio. Bismuth was described by Agricola in ''De Natura Fossilium'' (c. 1546); it had been confused in early times with tin and lead because of its resemblance to those elements. File:Arsen 1a.jpg, Arsenic, sealed in a container to prevent tarnishing File:Zinc fragment sublimed and 1cm3 cube.jpg, Zinc fragments and a 1 cm3 cube File:Antimony-4.jpg, Antimony, showing its brilliant lustre File:Wismut Kristall und 1cm3 Wuerfel.jpg, Bismuth in crystalline form, with a very thin oxidation layer, and a 1 cm3 bismuth cube


The Renaissance

The first systematic text on the arts of mining and metallurgy was De la pirotechnia, ''De la Pirotechnia'' (1540) by Vannoccio Biringuccio, which treats the examination, fusion, and working of metals. Sixteen years later, Georgius Agricola published ''De Re Metallica'' in 1556, a clear and complete account of the profession of mining, metallurgy, and the accessory arts and sciences, as well as qualifying as the greatest treatise on the chemical industry through the sixteenth century. He gave the following description of a metal in his ''De Natura Fossilium'' (1546):
Metal is a mineral body, by nature either liquid or somewhat hard. The latter may be melted by the heat of the fire, but when it has cooled down again and lost all heat, it becomes hard again and resumes its proper form. In this respect it differs from the stone which melts in the fire, for although the latter regain its hardness, yet it loses its pristine form and properties. Traditionally there are six different kinds of metals, namely gold, silver, copper, iron, tin and lead. There are really others, for Mercury (element), quicksilver is a metal, although the Alchemists disagree with us on this subject, and bismuth is also. The ancient Greek writers seem to have been ignorant of bismuth, wherefore Ammonius rightly states that there are many species of metals, animals, and plants which are unknown to us. Stibium when smelted in the crucible and refined has as much right to be regarded as a proper metal as is accorded to lead by writers. If when smelted, a certain portion be added to tin, a bookseller's alloy is produced from which the type is made that is used by those who print books on paper. Each metal has its own form which it preserves when separated from those metals which were mixed with it. Therefore neither electrum nor Stannum [not meaning our tin] is of itself a real metal, but rather an alloy of two metals. Electrum is an alloy of gold and silver, Stannum of lead and silver. And yet if silver be parted from the electrum, then gold remains and not electrum; if silver be taken away from Stannum, then lead remains and not Stannum. Whether brass, however, is found as a native metal or not, cannot be ascertained with any surety. We only know of the artificial brass, which consists of copper tinted with the colour of the mineral calamine. And yet if any should be dug up, it would be a proper metal. Black and white copper seem to be different from the red kind. Metal, therefore, is by nature either solid, as I have stated, or fluid, as in the unique case of quicksilver. But enough now concerning the simple kinds.Georgius Agricola
''De Re Metallica''
(1556) Tr. Herbert Clark Hoover & Lou Henry Hoover (1912); Footnote quoting ''De Natura Fossilium'' (1546), p. 180
Platinum, the third precious metal after gold and silver, was discovered in Ecuador during the period 1736 to 1744, by the Spanish astronomer Antonio de Ulloa and his colleague the mathematician Jorge Juan y Santacilia. Ulloa was the first person to write a scientific description of the metal, in 1748. In 1789, the German chemist Martin Heinrich Klaproth was able to isolate an oxide of uranium, which he thought was the metal itself. Klaproth was subsequently credited as the discoverer of uranium. It was not until 1841, that the French chemist Eugène-Melchior Péligot, was able to prepare the first sample of uranium metal. Henri Becquerel subsequently discovered radioactivity in 1896 by using uranium. In the 1790s, Joseph Priestley and the Dutch chemist Martinus van Marum observed the transformative action of metal surfaces on the dehydrogenation of alcohol, a development which subsequently led, in 1831, to the industrial scale synthesis of sulphuric acid using a platinum catalyst. In 1803, cerium was the first of the lanthanide metals to be discovered, in Bastnäs, Sweden by Jöns Jakob Berzelius and Wilhelm Hisinger, and independently by Martin Heinrich Klaproth in Germany. The lanthanide metals were largely regarded as oddities until the 1960s when methods were developed to more efficiently separate them from one another. They have subsequently found uses in cell phones, magnets, lasers, lighting, batteries, catalytic converters, and in other applications enabling modern technologies. Other metals discovered and prepared during this time were cobalt, nickel, manganese, molybdenum, tungsten, and chromium; and some of the platinum group metals, palladium, osmium, iridium, and rhodium.


Light metals

All metals discovered until 1809 had relatively high densities; their heaviness was regarded as a singularly distinguishing criterion. From 1809 onwards, light metals such as sodium, potassium, and strontium were isolated. Their low densities challenged conventional wisdom as to the nature of metals. They behaved chemically as metals however, and were subsequently recognised as such. Aluminum was discovered in 1824 but it was not until 1886 that an industrial large-scale production method was developed. Prices of aluminum dropped and aluminum became widely used in jewelry, everyday items, eyeglass frames, optical instruments, tableware, and foil in the 1890s and early 20th century. Aluminum's ability to form hard yet light alloys with other metals provided the metal many uses at the time. During World War I, major governments demanded large shipments of aluminum for light strong airframes. The most common metal in use for electric power transmission today is Aluminum-conductor steel-reinforced cable, aluminum-conductor steel-reinforced. Also seeing much use is all-aluminum-alloy conductor. Aluminum is used because it has about half the weight of a comparable resistance copper cable (though larger diameter due to lower specific conductivity), as well as being cheaper. Copper was more popular in the past and is still in use, especially at lower voltages and for grounding. While pure metallic titanium (99.9%) was first prepared in 1910 it was not used outside the laboratory until 1932. In the 1950s and 1960s, the Soviet Union pioneered the use of titanium in military and submarine applications as part of programs related to the Cold War. Starting in the early 1950s, titanium came into use extensively in military aviation, particularly in high-performance jets, starting with aircraft such as the F-100 Super Sabre and Lockheed A-12 and SR-71. Metallic scandium was produced for the first time in 1937. The first pound of 99% pure scandium metal was produced in 1960. Production of aluminum-scandium alloys began in 1971 following a U.S. patent. Aluminum-scandium alloys were also developed in the USSR. File:Na (Sodium).jpg, Sodium File:Potassium-2.jpg, Potassium pearls under paraffin oil. Size of the largest pearl is 0.5 cm. File:Strontium destilled crystals.jpg, Strontium crystals File:Aluminium-4.jpg, Aluminum chunk,
2.6 grams, File:Titan-crystal bar.JPG, A bar of titanium crystals File:Scandium sublimed dendritic and 1cm3 cube.jpg, Scandium, including a 1 cm3 cube


The age of steel

The modern era in steelmaking began with the introduction of Henry Bessemer's Bessemer process in 1855, the raw material for which was pig iron. His method let him produce steel in large quantities cheaply, thus mild steel came to be used for most purposes for which wrought iron was formerly used. The Gilchrist-Thomas process (or ''basic Bessemer process'') was an improvement to the Bessemer process, made by lining the converter with a basic (chemistry), basic material to remove phosphorus. Due to its high tensile strength and low cost, steel came to be a major component used in buildings, infrastructure, tools, ships, automobiles, machines, appliances, and weapons. In 1872, the Englishmen Clark and Woods patented an alloy that would today be considered a stainless steel. The corrosion resistance of iron-chromium alloys had been recognized in 1821 by French metallurgist Pierre Berthier. He noted their resistance against attack by some acids and suggested their use in cutlery. Metallurgists of the 19th century were unable to produce the combination of low carbon and high chromium found in most modern stainless steels, and the high-chromium alloys they could produce were too brittle to be practical. It was not until 1912 that the industrialisation of stainless steel alloys occurred in England, Germany, and the United States.


The last stable metallic elements

By 1900 three metals with atomic numbers less than lead (#82), the heaviest stable metal, remained to be discovered: elements 71, 72, 75. Von Welsbach, in 1906, proved that the old ytterbium also contained a new element (#71), which he named ''cassiopeium''. Urbain proved this simultaneously, but his samples were very impure and only contained trace quantities of the new element. Despite this, his chosen name ''lutetium'' was adopted. In 1908, Ogawa found element 75 in thorianite but assigned it as element 43 instead of 75 and named it ''nipponium''. In 1925 Walter Noddack, Ida Eva Tacke and Otto Berg announced its separation from gadolinite and gave it the present name, ''rhenium''. Georges Urbain claimed to have found element 72 in rare-earth residues, while Vladimir Vernadsky independently found it in orthite. Neither claim was confirmed due to World War I, and neither could be confirmed later, as the chemistry they reported does not match that now known for ''hafnium''. After the war, in 1922, Coster and Hevesy found it by X-ray spectroscopic analysis in Norwegian zircon. Hafnium was thus the last stable element to be discovered. File:Lutetium sublimed dendritic and 1cm3 cube.jpg, Lutetium, including a 1 cm3 cube File:Rhenium single crystal bar and 1cm3 cube.jpg, Rhenium, including a 1 cm3 cube File:Hf-crystal bar.jpg, Hafnium, in the form of a 1.7 kg bar By the end of World War II scientists had synthesized four post-uranium elements, all of which are radioactive (unstable) metals: neptunium (in 1940), plutonium (1940–41), and curium and americium (1944), representing elements 93 to 96. The first two of these were eventually found in nature as well. Curium and americium were by-products of the Manhattan project, which produced the world's first atomic bomb in 1945. The bomb was based on the nuclear fission of uranium, a metal first thought to have been discovered nearly 150 years earlier.


Post-World War II developments


Superalloys

Superalloys composed of combinations of Fe, Ni, Co, and Cr, and lesser amounts of W, Mo, Ta, Nb, Ti, and Al were developed shortly after World War II for use in high performance engines, operating at elevated temperatures (above 650 °C (1,200 °F)). They retain most of their strength under these conditions, for prolonged periods, and combine good low-temperature ductility with resistance to corrosion or oxidation. Superalloys can now be found in a wide range of applications including land, maritime, and aerospace turbines, and chemical and petroleum plants.


Transcurium metals

The successful development of the atomic bomb at the end of World War II sparked further efforts to synthesize new elements, nearly all of which are, or are expected to be, metals, and all of which are radioactive. It was not until 1949 that element 97 (berkelium), next after element 96 (curium), was synthesized by firing alpha particles at an americium target. In 1952, element 100 (fermium) was found in the debris of the first hydrogen bomb explosion; hydrogen, a nonmetal, had been identified as an element nearly 200 years earlier. Since 1952, elements 101 (mendelevium) to 118 (oganesson) have been synthesized.


Bulk metallic glasses

A metallic glass (also known as an amorphous or glassy metal) is a solid metallic material, usually an alloy, with disordered atomic-scale structure. Most pure and alloyed metals, in their solid state, have atoms arranged in a highly ordered crystalline structure. Amorphous metals have a non-crystalline glass-like structure. But unlike common glasses, such as window glass, which are typically electrical insulators, amorphous metals have good electrical conductivity. Amorphous metals are produced in several ways, including extremely rapid cooling, physical vapor deposition, solid-state reaction, ion irradiation, and mechanical alloying. The first reported metallic glass was an alloy (Au75Si25) produced at Caltech in 1960. More recently, batches of amorphous steel with three times the strength of conventional steel alloys have been produced. Currently the most important applications rely on the special magnetic properties of some ferromagnetic metallic glasses. The low magnetization loss is used in high efficiency transformers. Theft control ID tags and other article surveillance schemes often use metallic glasses because of these magnetic properties.


Shape-memory alloys

A shape-memory alloy (SMA) is an alloy that "remembers" its original shape and when deformed returns to its pre-deformed shape when heated. While the shape memory effect had been first observed in 1932, in an Au-Cd alloy, it was not until 1962, with the accidental discovery of the effect in a Ni-Ti alloy that research began in earnest, and another ten years before commercial applications emerged. SMA's have applications in robotics and automotive, aerospace and biomedical industries. There is another type of SMA, called a ferromagnetic shape-memory alloy (FSMA), that changes shape under strong magnetic fields. These materials are of particular interest as the magnetic response tends to be faster and more efficient than temperature-induced responses.


Quasicyrstalline alloys

In 1984, Israeli chemist Dan Shechtman found an aluminum-manganese alloy having five-fold symmetry, in breach of crystallographic convention at the time which said that crystalline structures could only have two-, three-, four-, or six-fold symmetry. Due to fear of the scientific community's reaction, it took him two years to publish the results for which he was awarded the Nobel Prize in Chemistry in 2011. Since this time, hundreds of quasicrystals have been reported and confirmed. They exist in many metallic alloys (and some polymers). Quasicrystals are found most often in aluminum alloys (Al-Li-Cu, Al-Mn-Si, Al-Ni-Co, Al-Pd-Mn, Al-Cu-Fe, Al-Cu-V, etc.), but numerous other compositions are also known (Cd-Yb, Ti-Zr-Ni, Zn-Mg-Ho, Zn-Mg-Sc, In-Ag-Yb, Pd-U-Si, etc.). Quasicrystals effectively have infinitely large unit cells. Icosahedrite Al63Cu24Fe13, the first quasicrystal found in nature, was discovered in 2009. Most quasicrystals have ceramic-like properties including low electrical conductivity (approaching values seen in insulators) and low thermal conductivity, high hardness, brittleness, and resistance to corrosion, and non-stick properties. Quasicrystals have been used to develop heat insulation, LEDs, diesel engines, and new materials that convert heat to electricity. New applications may take advantage of the low coefficient of friction and the hardness of some quasicrystalline materials, for example embedding particles in plastic to make strong, hard-wearing, low-friction plastic gears. Other potential applications include selective solar absorbers for power conversion, broad-wavelength reflectors, and bone repair and prostheses applications where biocompatibility, low friction and corrosion resistance are required.


Complex metallic alloys

Complex metallic alloys (CMAs) are intermetallic compounds characterized by large unit cells comprising some tens up to thousands of atoms; the presence of well-defined clusters of atoms (frequently with icosahedral symmetry); and partial disorder within their crystalline lattices. They are composed of two or more metallic elements, sometimes with metalloids or chalcogenides added. They include, for example, NaCd2, with 348 sodium atoms and 768 cadmium atoms in the unit cell. Linus Pauling attempted to describe the structure of NaCd2 in 1923, but did not succeed until 1955. At first called "giant unit cell crystals", interest in CMAs, as they came to be called, did not pick up until 2002, with the publication of a paper called "Structurally Complex Alloy Phases", given at the ''8th International Conference on Quasicrystals.'' Potential applications of CMAs include as heat insulation; solar heating; magnetic refrigerators; using waste heat to generate electricity; and coatings for turbine blades in military engines.


High entropy alloys

High entropy alloys (HEAs) such as AlLiMgScTi are composed of equal or nearly equal quantities of five or more metals. Compared to conventional alloys with only one or two base metals, HEAs have considerably better strength-to-weight ratios, higher tensile strength, and greater resistance to fracturing, corrosion, and oxidation. Although HEAs were described as early as 1981, significant interest did not develop until the 2010s; they continue to be the focus of research in materials science and engineering because of their potential for desirable properties.


MAX phase alloys

In a MAX phases, MAX phase alloy, M is an early transition metal, A is an A group element (mostly group IIIA and IVA, or groups 13 and 14), and X is either carbon or nitrogen. Examples are Hf2SnC and Ti4AlN3. Such alloys have some of the best properties of metals and ceramics. These properties include high electrical and thermal conductivity, thermal shock resistance, damage tolerance, machinability, high elastic stiffness, and low thermal expansion coefficients.Max phase composites
Materials Science and Engineering A
They can be polished to a metallic luster because of their excellent electrical conductivities. During mechanical testing, it has been found that polycrystalline Ti3SiC2 cylinders can be repeatedly compressed at room temperature, up to stresses of 1 GPa, and fully recover upon the removal of the load. Some MAX phases are also highly resistant to chemical attack (e.g. Ti3SiC2) and high-temperature oxidation in air (Ti2AlC, Cr2AlC2, and Ti3AlC2). Potential applications for MAX phase alloys include: as tough, machinable, thermal shock-resistant refractories; high-temperature heating elements; coatings for electrical contacts; and neutron irradiation resistant parts for nuclear applications. While MAX phase alloys were discovered in the 1960s, the first paper on the subject was not published until 1996.


See also

* Colored gold * Ductility * Ferrous metallurgy * Metal theft * Metallurgy * Metalworking * Properties of metals, metalloids and nonmetals * Structural steel * Transition metal


Notes


References


Further reading

* Matthew Choptuik, Choptuik M. W., Lehner L. & Pretorias F. 2015, "Probing strong-field gravity through numerical simulation", in Abhay Ashtekar, A. Ashtekar, Beverly Berger, B. K. Berger, J. Isenberg & M. MacCallum (eds), ''General Relativity and Gravitation: A Centennial Perspective'', Cambridge University Press, Cambridge, . * Cox P. A. 1997, ''The elements: Their origin, abundance and distribution,'' Oxford University Press, Oxford, * Crow J. M. 2016,
Impossible alloys: How to make never-before-seen metals
, ''New Scientist,'' 12 October * Hadhazy A. 2016,
Galactic 'gold mine' explains the origin of nature's heaviest elements
, ''Science Spotlights'', 10 May 2016, accessed 11 July 2016. * Hofmann S. 2002, ''On Beyond Uranium: Journey to the End of the Periodic Table'', Taylor & Francis, London, . * Thanu Padmanabhan, Padmanabhan T. 2001, ''Theoretical Astrophysics'', vol. 2, Stars and Stellar Systems, Cambridge University Press, Cambridge, . * Parish R. V. 1977, ''The metallic elements,'' Longman, London, * Podosek F. A. 2011, "Noble gases", in H. D. Holland & Karl Turekian, K. K. Turekian (eds), ''Isotope Geochemistry: From the Treatise on Geochemistry'', Elsevier, Amsterdam, pp. 467–492, . * Raymond R. 1984, ''Out of the fiery furnace: The impact of metals on the history of mankind,'' Macmillan Australia, Melbourne, * Rehder D. 2010, ''Chemistry in Space: From Interstellar Matter to the Origin of Life'', Wiley-VCH, Weinheim, . * Russell A. M. & Lee K. L. 2005, ''Structure–property relations in nonferrous metals,'' John Wiley & Sons, Hoboken, New Jersey, * Street A. & Alexander W. 1998, ''Metals in the service of man,'' 11th ed., Penguin Books, London, * Wilson A. J. 1994, ''The living rock: The tory of metals since earliest times and their impact on developing civilization'', Woodhead Publishing, Cambridge,


External links


ASM International
(formerly the American Society for Metals)
Strong as Titanium, Cheap as Dirt: New Steel Alloy Shines

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