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" or "America"
** Americans, citizens and nationals of the United States of America
** American ancestry, pe ...
and
Canadian English
Canadian English (CanE, CE, en-CA) encompasses the varieties of English native to Canada. According to the 2016 census, English was the first language of 19.4 million Canadians or 58.1% of the total population; the remainder spoke French ( ...
) 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 ...
Al 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 ...
13. Aluminium has a density lower than those of other common
metal
A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typicall ...
s, at approximately one third that of
steel
Steel is an alloy made up of iron with added carbon to improve its strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Stainless steels that are corrosion- and oxidation-resistant ty ...
. It has a great affinity towards
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
, and
forms a protective layer of
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 ...
on the surface when exposed to air. Aluminium visually resembles silver, both in its color and in its great ability to reflect light. It is soft,
non-magnetic
Magnetism is the class of physical attributes that are mediated by a magnetic field, which refers to the capacity to induce attractive and repulsive phenomena in other entities. Electric currents and the magnetic moments of elementary particles ...
and
ductile
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 ...
. It has one stable isotope,
27Al; this isotope is very common, making aluminium the twelfth most common element in the Universe. The radioactivity of
26Al is used in
radiodating
Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed. The method compares ...
.
Chemically, aluminium is a
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'', ...
in the
boron group
The boron group are the chemical elements in group 13 of the periodic table, comprising boron (B), aluminium (Al), gallium (Ga), indium (In), thallium (Tl), and nihonium (Nh). The elements in the boron group are characterized by having three vale ...
; as is common for the group, aluminium forms compounds primarily in the +3
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 ...
. The aluminium
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 ...
Al
3+ is small and highly charged; as such, it is polarizing, and
bonds aluminium forms tend towards
covalency. The strong affinity towards oxygen leads to aluminium's common association with oxygen in nature in the form of oxides; for this reason, aluminium is found on Earth primarily in rocks in the
crust, where it is the third most abundant element after
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
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 ...
, rather than in the
mantle, and virtually never as the free metal.
The discovery of aluminium was announced in 1825 by Danish physicist
Hans Christian Ørsted
Hans Christian Ørsted ( , ; often rendered Oersted in English; 14 August 17779 March 1851) was a Danish physicist and chemist who discovered that electric currents create magnetic fields, which was the first connection found between electricity ...
. The first industrial production of aluminium was initiated by French chemist
Henri Étienne Sainte-Claire Deville
Henri Étienne Sainte-Claire Deville (11 March 18181 July 1881) was a French chemist.
He was born in the island of St Thomas in the Danish West Indies, where his father was French consul. Together with his elder brother Charles he was educate ...
in 1856. Aluminium became much more available to the public with the
Hall–Héroult process
The Hall–Héroult process is the major industrial process for smelting aluminium. It involves dissolving aluminium oxide (alumina) (obtained most often from bauxite, aluminium's chief ore, through the Bayer process) in molten cryolite, and el ...
developed independently by French engineer
Paul Héroult
Paul (Louis-Toussaint) Héroult (10 April 1863 – 9 May 1914) was a French scientist. He was the inventor of the aluminium electrolysis and developed the first successful commercial electric arc furnace. He lived in Thury-Harcourt, Normandy.
...
and American engineer
Charles Martin Hall
Charles Martin Hall (December 6, 1863 – December 27, 1914) was an American inventor, businessman, and chemist. He is best known for his invention in 1886 of an inexpensive method for producing aluminum, which became the first metal to atta ...
in 1886, and the mass production of aluminium led to its extensive use in industry and everyday life. In World Wars
I and
II, aluminium was a crucial
strategic resource
In economics, factors of production, resources, or inputs are what is used in the production process to produce output—that is, goods and services. The utilized amounts of the various inputs determine the quantity of output according to the relat ...
for
aviation
Aviation includes the activities surrounding mechanical flight and the aircraft industry. ''Aircraft'' includes fixed-wing and rotary-wing types, morphable wings, wing-less lifting bodies, as well as lighter-than-air craft such as hot air ...
. In 1954, aluminium became the most produced
non-ferrous metal
In metallurgy, non-ferrous metals are metals or alloys that do not contain iron (allotropes of iron, ferrite, and so on) in appreciable amounts.
Generally more costly than ferrous metals, non-ferrous metals are used because of desirable proper ...
, surpassing
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
. In the 21st century, most aluminium was consumed in transportation, engineering, construction, and packaging in the United States, Western Europe, and Japan.
Despite its prevalence in the environment, no living organism is known to use aluminium
salts
In chemistry, a salt is a chemical compound consisting of an ionic assembly of positively charged cations and negatively charged anions, which results in a compound with no net electric charge. A common example is table salt, with positively cha ...
metabolically
Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cell ...
, but aluminium is well tolerated by plants and animals. Because of the abundance of these salts, the potential for a biological role for them is of interest, and studies continue.
Physical characteristics
Isotopes
Of aluminium isotopes, only is stable. This situation is common for elements with an odd atomic number. It is the only
primordial aluminium isotope, i.e. the only one that has existed on Earth in its current form since the formation of the planet. Nearly all aluminium on Earth is present as this isotope, which makes it a
mononuclidic element
A mononuclidic element or monotopic element is one of the 21 chemical elements that is found naturally on Earth essentially as a single nuclide (which may, or may not, be a stable nuclide). This single nuclide will have a characteristic atomic m ...
and means that its
standard atomic weight is virtually the same as that of the isotope. This makes aluminium very useful in
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 ...
(NMR), as its single stable isotope has a high NMR sensitivity. The standard atomic weight of aluminium is low in comparison with many other metals.
All other isotopes of aluminium are
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 containing unstable nuclei is consid ...
. The most stable of these is
26Al: while it was present along with stable
27Al in the interstellar medium from which the Solar System formed, having been produced by
stellar nucleosynthesis
Stellar nucleosynthesis is the creation (nucleosynthesis) of chemical elements by nuclear fusion reactions within stars. Stellar nucleosynthesis has occurred since the original creation of hydrogen, helium and lithium during the Big Bang. As a ...
as well, its
half-life
Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable ato ...
is only 717,000 years and therefore a detectable amount has not survived since the formation of the planet. However, minute traces of
26Al are produced from
argon
Argon is a chemical element with the symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third-most abundant gas in Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice as abu ...
in the
atmosphere
An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A s ...
by
spallation
Spallation is a process in which fragments of material (spall) are ejected from a body due to impact or stress. In the context of impact mechanics it describes ejection of material from a target during impact by a projectile. In planetary p ...
caused by
cosmic ray
Cosmic rays are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our own ...
protons. The ratio of
26Al to
10Be has been used for
radiodating
Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed. The method compares ...
of geological processes over 10
5 to 10
6 year time scales, in particular transport, deposition,
sediment
Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand an ...
storage, burial times, and erosion. Most meteorite scientists believe that the energy released by the decay of
26Al was responsible for the melting and
differentiation of some
asteroids
An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere.
...
after their formation 4.55 billion years ago.
The remaining isotopes of aluminium, with
mass number
The mass number (symbol ''A'', from the German word ''Atomgewicht'' tomic weight, also called atomic mass number or nucleon number, is the total number of protons and neutrons (together known as nucleons) in an atomic nucleus. It is approxima ...
s ranging from 22 to 43, all have half-lives well under an hour. Three
metastable
In chemistry and physics, metastability denotes an intermediate Energy level, energetic state within a dynamical system other than the system's ground state, state of least energy.
A ball resting in a hollow on a slope is a simple example of me ...
states are known, all with half-lives under a minute.
Electron shell
An aluminium atom has 13 electrons, 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 , with three electrons beyond a stable noble gas configuration. Accordingly, the combined first three
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 ...
of aluminium are far lower than the fourth ionization energy alone. Such an electron configuration is shared with the other well-characterized members of its group,
boron
Boron is a chemical element with the symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the ''boron group'' it has th ...
,
gallium
Gallium is a chemical element with the symbol Ga and atomic number 31. Discovered by French chemist Paul-Émile Lecoq de Boisbaudran in 1875, Gallium is in group 13 of the periodic table and is similar to the other metals of the group (aluminiu ...
,
indium
Indium is a chemical element with the symbol In and atomic number 49. Indium is the softest metal that is not an alkali metal. It is a silvery-white metal that resembles tin in appearance. It is a post-transition metal that makes up 0.21 parts p ...
, and
thallium
Thallium is a chemical element with the Symbol (chemistry), symbol Tl and atomic number 81. It is a gray post-transition metal that is not found free in nature. When isolated, thallium resembles tin, but discolors when exposed to air. Chemists W ...
; it is also expected for
nihonium
Nihonium is a synthetic chemical element with the symbol Nh and atomic number 113. It is extremely radioactive; its most stable known isotope, nihonium-286, has a half-life of about 10 seconds. In the periodic table, nihonium is a transactinid ...
. Aluminium can relatively easily surrender its three outermost electrons in many chemical reactions (see
below
Below may refer to:
*Earth
*Ground (disambiguation)
*Soil
*Floor
*Bottom (disambiguation)
Bottom may refer to:
Anatomy and sex
* Bottom (BDSM), the partner in a BDSM who takes the passive, receiving, or obedient role, to that of the top or ...
). The
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 ...
of aluminium is 1.61 (Pauling scale).
![Aluminium Atomic lattice](https://upload.wikimedia.org/wikipedia/commons/d/d9/Aluminium_Atomic_lattice.png)
A free aluminium atom has a
radius
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 ...
of 143
pm. With the three outermost electrons removed, the
radius
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 ...
shrinks to 39 pm for a 4-coordinated atom or 53.5 pm for a 6-coordinated atom. At
standard temperature and pressure
Standard temperature and pressure (STP) are standard sets of conditions for experimental measurements to be established to allow comparisons to be made between different sets of data. The most used standards are those of the International Union o ...
, aluminium atoms (when not affected by atoms of other elements) form a
face-centered cubic crystal system bound by
metallic bonding
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 ...
provided by atoms' outermost electrons; hence aluminium (at these conditions) is a metal.
This crystal system is shared by many other metals, such as
lead
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 cu ...
and
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
; the size of a unit cell of aluminium is comparable to that of those other metals.
[
] The system, however, is not shared by the other members of its group; boron has ionization energies too high to allow metallization, thallium has a
hexagonal close-packed
In geometry, close-packing of equal spheres is a dense arrangement of congruent spheres in an infinite, regular arrangement (or lattice). Carl Friedrich Gauss proved that the highest average density – that is, the greatest fraction of space occu ...
structure, and gallium and indium have unusual structures that are not close-packed like those of aluminium and thallium. The few electrons that are available for
metallic bonding
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 aluminium metal are a probable cause for it being soft with a low melting point and low
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 ...
.
[Greenwood and Earnshaw, pp. 222–4]
Bulk
Aluminium metal has an appearance ranging from silvery white to dull gray, depending on the
surface roughness
Surface roughness, often shortened to roughness, is a component of surface finish (surface texture). It is quantified by the deviations in the direction of the normal vector of a real surface from its ideal form. If these deviations are large, ...
. Aluminium mirrors are the most reflective of all metal mirrors for the near
ultraviolet
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...
and far
infrared
Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...
light, and one of the most reflective in the visible spectrum, nearly on par with silver, and the two therefore look similar. Aluminium is also good at reflecting
solar radiation
Solar irradiance is the power per unit area (surface power density) received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument.
Solar irradiance is measured in watts per square metre (W/m ...
, although prolonged exposure to sunlight in air adds wear to the surface of the metal; this may be prevented if aluminium is
anodized
Anodizing is an electrolytic passivation process used to increase the thickness of the natural oxide layer on the surface of metal parts.
The process is called ''anodizing'' because the part to be treated forms the anode electrode of an electro ...
, which adds a protective layer of oxide on the surface.
The density of aluminium is 2.70 g/cm
3, about 1/3 that of steel, much lower than other commonly encountered metals, making aluminium parts easily identifiable through their lightness. Aluminium's low density compared to most other metals arises from the fact that its nuclei are much lighter, while difference in the unit cell size does not compensate for this difference. The only lighter metals are the metals of
groups 1 and
2, which apart from
beryllium
Beryllium is a chemical element with the symbol Be and atomic number 4. It is a steel-gray, strong, lightweight and brittle alkaline earth metal. It is a divalent element that occurs naturally only in combination with other elements to form mi ...
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 ...
are too reactive for structural use (and beryllium is very toxic). Aluminium is not as strong or stiff as steel, but the low density makes up for this in the
aerospace
Aerospace is a term used to collectively refer to the atmosphere and outer space. Aerospace activity is very diverse, with a multitude of commercial, industrial and military applications. Aerospace engineering consists of aeronautics and astrona ...
industry and for many other applications where light weight and relatively high strength are crucial.
Pure aluminium is quite soft and lacking in strength. In most applications various
aluminium alloys
An aluminium alloy (or aluminum alloy; see spelling differences) is an alloy in which aluminium (Al) is the predominant metal. The typical alloying elements are copper, magnesium, manganese, silicon, tin, nickel and zinc. There are two principal ...
are used instead because of their higher strength and hardness. The
yield strength
In materials science and engineering, the yield point is the point on a stress-strain curve that indicates the limit of elastic behavior and the beginning of plastic behavior. Below the yield point, a material will deform elastically and wi ...
of pure aluminium is 7–11
MPa
MPA or mPa may refer to:
Academia
Academic degrees
* Master of Performing Arts
* Master of Professional Accountancy
* Master of Public Administration
* Master of Public Affairs
Schools
* Mesa Preparatory Academy
* Morgan Park Academy
* Mou ...
, while
aluminium alloy
An aluminium alloy (or aluminum alloy; see spelling differences) is an alloy in which aluminium (Al) is the predominant metal. The typical alloying elements are copper, magnesium, manganese, silicon, tin, nickel and zinc. There are two principal ...
s have yield strengths ranging from 200 MPa to 600 MPa.
[
] Aluminium is
ductile
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 ...
, with a percent elongation of 50-70%,
[
] 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 ...
allowing it to be easily
drawn and
extruded
Extrusion is a process used to create objects of a fixed cross-sectional profile by pushing material through a die of the desired cross-section. Its two main advantages over other manufacturing processes are its ability to create very complex c ...
. It is also easily
machined
Machining is a process in which a material (often metal) is cut to a desired final shape and size by a controlled material-removal process. The processes that have this common theme are collectively called subtractive manufacturing, which utilizes ...
and
cast
Cast may refer to:
Music
* Cast (band), an English alternative rock band
* Cast (Mexican band), a progressive Mexican rock band
* The Cast, a Scottish musical duo: Mairi Campbell and Dave Francis
* ''Cast'', a 2012 album by Trespassers William
* ...
.
Aluminium is an excellent
thermal
A thermal column (or thermal) is a rising mass of buoyant air, a convective current in the atmosphere, that transfers heat energy vertically. Thermals are created by the uneven heating of Earth's surface from solar radiation, and are an example ...
and
electrical conductor
In physics and electrical engineering, a conductor is an object or type of material that allows the flow of charge (electric current) in one or more directions. Materials made of metal are common electrical conductors. Electric current is gener ...
, having around 60% the conductivity of
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
, both thermal and electrical, while having only 30% of copper's density. Aluminium is capable of
superconductivity
Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic flux fields are expelled from the material. Any material exhibiting these properties is a superconductor. Unlike ...
, with a superconducting critical temperature of 1.2
kelvin
The kelvin, symbol K, is the primary unit of temperature in the International System of Units (SI), used alongside its prefixed forms and the degree Celsius. It is named after the Belfast-born and University of Glasgow-based engineer and phys ...
and a critical magnetic field of about 100
gauss
Johann Carl Friedrich Gauss (; german: Gauß ; la, Carolus Fridericus Gauss; 30 April 177723 February 1855) was a German mathematician and physicist who made significant contributions to many fields in mathematics and science. Sometimes refer ...
(10
millitesla
The tesla (symbol: T) is the unit of magnetic flux density (also called magnetic B-field strength) in the International System of Units (SI).
One tesla is equal to one weber per square metre. The unit was announced during the General Conferenc ...
s). It is
paramagnetic
Paramagnetism is a form of magnetism whereby some materials are weakly attracted by an externally applied magnetic field, and form internal, induced magnetic fields in the direction of the applied magnetic field. In contrast with this behavior, d ...
and thus essentially unaffected by static magnetic fields. The high electrical conductivity, however, means that it is strongly affected by alternating magnetic fields through the induction of
eddy currents
Eddy currents (also called Foucault's currents) are loops of electrical current induced within conductors by a changing magnetic field in the conductor according to Faraday's law of induction or by the relative motion of a conductor in a magn ...
.
Chemistry
Aluminium combines characteristics of pre- and post-transition metals. Since it has few available electrons for metallic bonding, like its heavier
group 13
The Group 13 network ( pl, Trzynastka, Yiddish: ''דאָס דרײַצענטל'') was a Jewish Nazi collaborationist organization in the Warsaw Ghetto during the German occupation of Poland in World War II. The rise and fall of the Group ...
congeners, it has the characteristic physical properties of a post-transition metal, with longer-than-expected interatomic distances.
Furthermore, as Al
3+ is a small and highly charged cation, it is strongly polarizing and
bonding in aluminium compounds tends towards
covalency; this behavior is similar to that of
beryllium
Beryllium is a chemical element with the symbol Be and atomic number 4. It is a steel-gray, strong, lightweight and brittle alkaline earth metal. It is a divalent element that occurs naturally only in combination with other elements to form mi ...
(Be
2+), and the two display an example of a
diagonal relationship
A diagonal relationship is said to exist between certain pairs of diagonally adjacent elements in the second and third periods (first 20 elements) of the periodic table. These pairs (lithium (Li) and magnesium (Mg), beryllium (Be) and aluminium ...
.
The underlying core under aluminium's valence shell is that of the preceding
noble gas
The noble gases (historically also the inert gases; sometimes referred to as aerogens) make up a class of chemical elements with similar properties; under standard conditions, they are all odorless, colorless, monatomic gases with very low chemi ...
, whereas those of its heavier congeners
gallium
Gallium is a chemical element with the symbol Ga and atomic number 31. Discovered by French chemist Paul-Émile Lecoq de Boisbaudran in 1875, Gallium is in group 13 of the periodic table and is similar to the other metals of the group (aluminiu ...
,
indium
Indium is a chemical element with the symbol In and atomic number 49. Indium is the softest metal that is not an alkali metal. It is a silvery-white metal that resembles tin in appearance. It is a post-transition metal that makes up 0.21 parts p ...
,
thallium
Thallium is a chemical element with the Symbol (chemistry), symbol Tl and atomic number 81. It is a gray post-transition metal that is not found free in nature. When isolated, thallium resembles tin, but discolors when exposed to air. Chemists W ...
, and
nihonium
Nihonium is a synthetic chemical element with the symbol Nh and atomic number 113. It is extremely radioactive; its most stable known isotope, nihonium-286, has a half-life of about 10 seconds. In the periodic table, nihonium is a transactinid ...
also include a filled d-subshell and in some cases a filled f-subshell. Hence, the inner electrons of aluminium shield the valence electrons almost completely, unlike those of aluminium's heavier congeners. As such, aluminium is the most electropositive metal in its group, and its hydroxide is in fact more basic than that of gallium. Aluminium also bears minor similarities to the metalloid boron in the same group: AlX
3 compounds are valence
isoelectronic
Isoelectronicity is a phenomenon observed when two or more molecules have the same structure (positions and connectivities among atoms) and the same electronic configurations, but differ by what specific elements are at certain locations in the ...
to BX
3 compounds (they have the same valence electronic structure), and both behave as
Lewis acid
A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any sp ...
s and readily form
adduct
An adduct (from the Latin ''adductus'', "drawn toward" alternatively, a contraction of "addition product") is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all co ...
s. Additionally, one of the main motifs of boron chemistry is
regular icosahedral structures, and aluminium forms an important part of many icosahedral
quasicrystal
A quasiperiodic crystal, or quasicrystal, is a structure that is ordered but not periodic. A quasicrystalline pattern can continuously fill all available space, but it lacks translational symmetry. While crystals, according to the classical cr ...
alloys, including the Al–Zn–Mg class.
Aluminium has a high
chemical affinity In chemical physics and physical chemistry, chemical affinity is the electronic property by which dissimilar chemical species are capable of forming chemical compounds. Chemical affinity can also refer to the tendency of an atom or compound to co ...
to oxygen, which renders it suitable for use as a
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 ...
in the
thermite
Thermite () is a pyrotechnic composition of metal powder and metal oxide. When ignited by heat or chemical reaction, thermite undergoes an exothermic reduction-oxidation (redox) reaction. Most varieties are not explosive, but can create brief ...
reaction. A fine powder of aluminium metal reacts explosively on contact with
liquid oxygen
Liquid oxygen—abbreviated LOx, LOX or Lox in the aerospace, submarine and gas industries—is the liquid form of molecular oxygen. It was used as the oxidizer in the first liquid-fueled rocket invented in 1926 by Robert H. Goddard, an applica ...
; under normal conditions, however, aluminium forms a thin oxide layer (~5 nm at room temperature) that protects the metal from further corrosion by oxygen, water, or dilute acid, a process termed
passivation.
[
] Because of its general resistance to corrosion, aluminium is one of the few metals that retains silvery reflectance in finely powdered form, making it an important component of
silver-colored paints. Aluminium is not attacked by oxidizing acids because of its passivation. This allows aluminium to be used to store reagents such as
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 ...
, concentrated
sulfuric acid
Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...
, and some organic acids.
In hot concentrated
hydrochloric acid
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
Acid strength is the tendency of an acid, symbol ...
, aluminium reacts with water with evolution of hydrogen, and in aqueous
sodium hydroxide
Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations and hydroxide anions .
Sodium hydroxide is a highly caustic base and alkali ...
or
potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash.
Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which exp ...
at room temperature to form
aluminates
In chemistry, an aluminate is a compound containing an oxyanion of aluminium, such as sodium aluminate. In the naming of inorganic compounds, it is a suffix that indicates a polyatomic anion with a central aluminum atom.
Aluminate oxyanions
Alum ...
—protective passivation under these conditions is negligible.
Aqua regia also dissolves aluminium.
Aluminium is corroded by dissolved
chlorides
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 ...
, such as common
sodium chloride
Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35.45 g ...
, which is why household plumbing is never made from aluminium.
The oxide layer on aluminium is also destroyed by contact with
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 ...
due to
amalgamation
Amalgamation is the process of combining or uniting multiple entities into one form.
Amalgamation, amalgam, and other derivatives may refer to:
Mathematics and science
* Amalgam (chemistry), the combination of mercury with another metal
**Pan am ...
or with salts of some electropositive metals. As such, the strongest aluminium alloys are less corrosion-resistant due to
galvanic reactions with alloyed
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
,
and aluminium's corrosion resistance is greatly reduced by aqueous salts, particularly in the presence of dissimilar metals.
Aluminium reacts with most nonmetals upon heating, forming compounds such as
aluminium nitride (AlN),
aluminium sulfide
Aluminum sulfide or aluminium sulphide is a chemical compound with the formula Al2 S3. This colorless species has an interesting structural chemistry, existing in several forms. The material is sensitive to moisture, hydrolyzing to hydrated alumi ...
(Al
2S
3), and the aluminium halides (AlX
3). It also forms a wide range of
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 bonding, metallic alloy that forms an ordered solid-state Chemical compound, compoun ...
s involving metals from every group on the periodic table.
Inorganic compounds
The vast majority of compounds, including all aluminium-containing minerals and all commercially significant aluminium compounds, feature aluminium in the oxidation state 3+. The
coordination number
In chemistry, crystallography, and materials science, the coordination number, also called ligancy, of a central atom in a molecule or crystal is the number of atoms, molecules or ions bonded to it. The ion/molecule/atom surrounding the central i ...
of such compounds varies, but generally Al
3+ is either six- or four-coordinate. Almost all compounds of aluminium(III) are colorless.
![AlHydrolysis](https://upload.wikimedia.org/wikipedia/commons/8/83/AlHydrolysis.png)
In aqueous solution, Al
3+ exists as the hexaaqua cation
2O)6">l(H2O)6sup>3+, which has an approximate
Ka of 10
−5. Such solutions are acidic as this cation can act as a proton donor and progressively
hydrolyze
Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile.
Biological hydrolysis ...
until a
precipitate
In an aqueous solution, precipitation is the process of transforming a dissolved substance into an insoluble solid from a super-saturated solution. The solid formed is called the precipitate. In case of an inorganic chemical reaction leading ...
of
aluminium hydroxide
Aluminium hydroxide, Al(OH)3, is found in nature as the mineral gibbsite (also known as hydrargillite) and its three much rarer polymorphs: bayerite, doyleite, and nordstrandite. Aluminium hydroxide is amphoteric, i.e., it has both basic and ...
, Al(OH)
3, forms. This is useful for
clarification of water, as the precipitate nucleates on
suspended particles in the water, hence removing them. Increasing the pH even further leads to the hydroxide dissolving again as
aluminate
In chemistry, an aluminate is a compound containing an oxyanion of aluminium, such as sodium aluminate. In the naming of inorganic compounds, it is a suffix that indicates a polyatomic ion, polyatomic anion with a central aluminum atom.
Aluminate ...
,
2O)2(OH)4">l(H2O)2(OH)4sup>−, is formed.
Aluminium hydroxide forms both salts and aluminates and dissolves in acid and alkali, as well as on fusion with acidic and basic oxides. This behavior of Al(OH)
3 is termed
amphoterism
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 ...
and is characteristic of weakly basic cations that form insoluble hydroxides and whose hydrated species can also donate their protons. One effect of this is that aluminium salts with weak acids are hydrolyzed in water to the aquated hydroxide and the corresponding nonmetal hydride: for example,
aluminium sulfide
Aluminum sulfide or aluminium sulphide is a chemical compound with the formula Al2 S3. This colorless species has an interesting structural chemistry, existing in several forms. The material is sensitive to moisture, hydrolyzing to hydrated alumi ...
yields
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 ...
. However, some salts like
aluminium carbonate
Aluminium carbonate (Al2(CO3)3), is a carbonate of aluminium. It is not well characterized; one authority says that simple carbonates of aluminium are not known.Anthony John Downs, (1993), ''Chemistry of Aluminium, Gallium, Indium, and Thallium'', ...
exist in aqueous solution but are unstable as such; and only incomplete hydrolysis takes place for salts with strong acids, such as the halides,
nitrate
Nitrate is a polyatomic ion
A polyatomic ion, also known as a molecular ion, is a covalent bonded set of two or more atoms, or of a metal complex, that can be considered to behave as a single unit and that has a net charge that is not zer ...
, and
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 ...
. For similar reasons, anhydrous aluminium salts cannot be made by heating their "hydrates": hydrated aluminium chloride is in fact not AlCl
3·6H
2O but
2O)6">l(H2O)6l
3, and the Al–O bonds are so strong that heating is not sufficient to break them and form Al–Cl bonds instead:
:2
2O)6">l(H2O)6l
3 Al
2O
3 + 6 HCl + 9 H
2O
All four
trihalides are well known. Unlike the structures of the three heavier trihalides,
aluminium fluoride
Aluminium fluoride refers to inorganic compounds with the formula AlF3·''x''H2O. They are all colorless solids. Anhydrous AlF3 is used in the production of aluminium metal. Several occur as minerals.
Occurrence and production
Aside from anhydr ...
(AlF
3) features six-coordinate aluminium, which explains its involatility and insolubility as well as high
heat of formation
In chemistry and thermodynamics, the standard enthalpy of formation or standard heat of formation of a compound is the change of enthalpy during the formation of 1 mole of the substance from its constituent elements in their reference state, wit ...
. Each aluminium atom is surrounded by six fluorine atoms in a distorted
octahedral
In geometry, an octahedron (plural: octahedra, octahedrons) is a polyhedron with eight faces. The term is most commonly used to refer to the regular octahedron, a Platonic solid composed of eight equilateral triangles, four of which meet at ea ...
arrangement, with each fluorine atom being shared between the corners of two octahedra. Such units also exist in complex fluorides such as
cryolite
Cryolite ( Na3 Al F6, sodium hexafluoroaluminate) is an uncommon mineral identified with the once-large deposit at Ivittuut on the west coast of Greenland, mined commercially until 1987.
History
Cryolite was first described in 1798 by Danish vete ...
, Na
3AlF
6. AlF
3 melts at and is made by reaction of
aluminium oxide with
hydrogen fluoride
Hydrogen fluoride (fluorane) is an inorganic compound with the chemical formula . This colorless gas or liquid is the principal industrial source of fluorine, often as an aqueous solution called hydrofluoric acid. It is an important feedstock i ...
gas at .
With heavier halides, the coordination numbers are lower. The other trihalides are
dimeric or
polymer
A polymer (; Greek '' poly-'', "many" + ''-mer'', "part")
is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...
ic with tetrahedral four-coordinate aluminium centers.
Aluminium trichloride
Aluminium chloride, also known as aluminium trichloride, is an inorganic compound with the formula . It forms hexahydrate with the formula , containing six water molecules of hydration. Both are colourless crystals, but samples are often contam ...
(AlCl
3) has a layered polymeric structure below its melting point of but transforms on melting to Al
2Cl
6 dimers. At higher temperatures those increasingly dissociate into trigonal planar AlCl
3 monomers similar to the structure of
BCl3.
Aluminium tribromide
Aluminium bromide is any chemical compound with the empirical formula AlBrx. Aluminium tribromide is the most common form of aluminium bromide. It is a colorless, sublimable hygroscopic solid; hence old samples tend to be hydrated, mostly as al ...
and
aluminium triiodide
Aluminium iodide is a chemical compound containing aluminium and iodine. Invariably, the name refers to a compound of the composition , formed by the reaction of aluminium and iodine or the action of on metal. The hexahydrate is obtained f ...
form Al
2X
6 dimers in all three phases and hence do not show such significant changes of properties upon phase change. These materials are prepared by treating aluminium metal with the halogen. The aluminium trihalides form many
addition compound
An adduct (from the Latin ''adductus'', "drawn toward" alternatively, a contraction of "addition product") is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all co ...
s or complexes; their
Lewis acid
A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any sp ...
ic nature makes them useful as
catalysts
Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
for the
Friedel–Crafts reaction
The Friedel–Crafts reactions are a set of reactions developed by Charles Friedel and James Crafts in 1877 to attach substituents to an aromatic ring. Friedel–Crafts reactions are of two main types: alkylation reactions and acylation reactions ...
s. Aluminium trichloride has major industrial uses involving this reaction, such as in the manufacture of
anthraquinone
Anthraquinone, also called anthracenedione or dioxoanthracene, is an aromatic organic compound with formula . Isomers include various quinone derivatives. The term anthraquinone however refers to the isomer, 9,10-anthraquinone (IUPAC: 9,10-dioxo ...
s and
styrene
Styrene () is an organic compound with the chemical formula C6H5CH=CH2. This derivative of benzene is a colorless oily liquid, although aged samples can appear yellowish. The compound evaporates easily and has a sweet smell, although high concen ...
; it is also often used as the precursor for many other aluminium compounds and as a reagent for converting nonmetal fluorides into the corresponding chlorides (a
transhalogenation reaction).
Aluminium forms one stable oxide with the
chemical formula
In chemistry, a chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, ...
Al
2O
3, commonly called
alumina. It can be found in nature in the mineral
corundum
Corundum is a crystalline form of aluminium oxide () typically containing traces of iron, titanium, vanadium and chromium. It is a rock-forming mineral. It is a naturally transparent material, but can have different colors depending on the pres ...
, α-alumina; there is also a γ-alumina phase. Its crystalline form,
corundum
Corundum is a crystalline form of aluminium oxide () typically containing traces of iron, titanium, vanadium and chromium. It is a rock-forming mineral. It is a naturally transparent material, but can have different colors depending on the pres ...
, is very hard (
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 ...
9), has a high melting point of , has very low volatility, is chemically inert, and a good electrical insulator, it is often used in abrasives (such as toothpaste), as a refractory material, and in
ceramics
A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain ...
, as well as being the starting material for the electrolytic production of aluminium metal.
Sapphire
Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide () with trace amounts of elements such as iron, titanium, chromium, vanadium, or magnesium. The name sapphire is derived via the Latin "sapphir ...
and
ruby
A ruby is a pinkish red to blood-red colored gemstone, a variety of the mineral corundum ( aluminium oxide). Ruby is one of the most popular traditional jewelry gems and is very durable. Other varieties of gem-quality corundum are called sa ...
are impure corundum contaminated with trace amounts of other metals. The two main oxide-hydroxides, AlO(OH), are
boehmite
Boehmite or böhmite is an aluminium oxide hydroxide (γ-AlO(OH)) mineral, a component of the aluminium ore bauxite. It is dimorphous with diaspore. It crystallizes in the orthorhombic dipyramidal system and is typically massive in habit. It is ...
and
diaspore
Diaspore , also known as diasporite, empholite, kayserite, or tanatarite, is an aluminium oxide hydroxide mineral, α-AlO(OH), crystallizing in the orthorhombic system and isomorphous with goethite. It occurs sometimes as flattened crystals, bu ...
. There are three main trihydroxides:
bayerite,
gibbsite
Gibbsite, Al(OH)3, is one of the mineral forms of aluminium hydroxide. It is often designated as γ-Al(OH)3 (but sometimes as α-Al(OH)3.). It is also sometimes called hydrargillite (or hydrargyllite).
Gibbsite is an important ore of aluminiu ...
, and
nordstrandite, which differ in their crystalline structure (
polymorphs). Many other intermediate and related structures are also known. Most are produced from ores by a variety of wet processes using acid and base. Heating the hydroxides leads to formation of corundum. These materials are of central importance to the production of aluminium and are themselves extremely useful. Some mixed oxide phases are also very useful, such as
spinel
Spinel () is the magnesium/aluminium member of the larger spinel group of minerals. It has the formula in the cubic crystal system. Its name comes from the Latin word , which means ''spine'' in reference to its pointed crystals.
Properties
S ...
(MgAl
2O
4), Na-β-alumina (NaAl
11O
17), and
tricalcium aluminate
Tricalcium aluminate Ca3Al2O6, often formulated as 3CaO·Al2O3 to highlight the proportions of the oxides from which it is made, is the most basic of the calcium aluminates. It does not occur in nature, but is an important mineral phase in Portl ...
(Ca
3Al
2O
6, an important mineral phase in
Portland cement
Portland cement is the most common type of cement in general use around the world as a basic ingredient of concrete, mortar, stucco, and non-specialty grout. It was developed from other types of hydraulic lime in England in the early 19th c ...
).
The only stable
chalcogenide : 220px, Cadmium sulfide, a prototypical metal chalcogenide, is used as a yellow pigment.
A chalcogenide is a chemical compound consisting of at least one chalcogen anion and at least one more electropositive element. Although all group 16 elements ...
s under normal conditions are
aluminium sulfide
Aluminum sulfide or aluminium sulphide is a chemical compound with the formula Al2 S3. This colorless species has an interesting structural chemistry, existing in several forms. The material is sensitive to moisture, hydrolyzing to hydrated alumi ...
(Al
2S
3),
selenide A selenide is a chemical compound containing a selenium anion with oxidation number of −2 (Se2−), much as sulfur does in a sulfide. The chemistry of the selenides and sulfides is similar. Similar to sulfide, in aqueous solution, the selenide ion ...
(Al
2Se
3), and
telluride (Al
2Te
3). All three are prepared by direct reaction of their elements at about and quickly hydrolyze completely in water to yield aluminium hydroxide and the respective
hydrogen chalcogenide Hydrogen chalcogenides (also chalcogen hydrides or hydrogen chalcides) are binary compounds of hydrogen with chalcogen atoms (elements of group 16: oxygen, sulfur, selenium, tellurium, and polonium). Water, the first chemical compound in this series ...
. As aluminium is a small atom relative to these chalcogens, these have four-coordinate tetrahedral aluminium with various polymorphs having structures related to
wurtzite
Wurtzite is a zinc and iron sulfide mineral with the chemical formula , a less frequently encountered Polymorphism (materials science), structural polymorph form of sphalerite. The iron content is variable up to eight percent.Palache, Charles, Har ...
, with two-thirds of the possible metal sites occupied either in an orderly (α) or random (β) fashion; the sulfide also has a γ form related to γ-alumina, and an unusual high-temperature hexagonal form where half the aluminium atoms have tetrahedral four-coordination and the other half have trigonal bipyramidal five-coordination.
Four
pnictide
A pnictogen ( or ; from grc, πνῑ́γω "to choke" and -gen, "generator") is any of the chemical elements in group 15 of the periodic table. Group 15 is also known as the nitrogen group or nitrogen family. Group 15 consists of the el ...
s –
aluminium nitride (AlN),
aluminium phosphide
Aluminium phosphide is a highly toxic inorganic compound with the chemical formula AlP, used as a wide band gap semiconductor and a fumigant. This colorless solid is generally sold as a grey-green-yellow powder due to the presence of impurities a ...
(AlP),
aluminium arsenide (AlAs), and
aluminium antimonide
Aluminium antimonide (AlSb) is a semiconductor of the group III-V family containing aluminium and antimony. The lattice constant is 0.61 nm. The indirect bandgap is approximately 1.6 electron volt, eV at 300 K, whereas the direct band gap is ...
(AlSb) – are known. They are all
III-V semiconductor
Semiconductor materials are nominally small band gap insulators. The defining property of a semiconductor material is that it can be compromised by doping it with impurities that alter its electronic properties in a controllable way.
Because of t ...
s isoelectronic to
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 ...
and
germanium
Germanium is a chemical element with the symbol Ge and atomic number 32. It is lustrous, hard-brittle, grayish-white and similar in appearance to silicon. It is a metalloid in the carbon group that is chemically similar to its group neighbors s ...
, all of which but AlN have the
zinc blende
Sphalerite (sometimes spelled sphaelerite) is a sulfide mineral with the chemical formula . It is the most important ore of zinc. Sphalerite is found in a variety of deposit types, but it is primarily in sedimentary exhalative, Mississippi-Va ...
structure. All four can be made by high-temperature (and possibly high-pressure) direct reaction of their component elements.
Aluminium alloys well with most other metals (with the exception of most
alkali metals
The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K),The symbols Na and K for sodium and potassium are derived from their Latin names, ''natrium'' and ''kalium''; these are still the origins of the names ...
and group 13 metals) and over 150
intermetallics
An intermetallic (also called an intermetallic compound, intermetallic alloy, ordered intermetallic alloy, and a long-range-ordered alloy) is a type of metallic alloy that forms an ordered solid-state compound between two or more metallic elemen ...
with other metals are known. Preparation involves heating fixed metals together in certain proportion, followed by gradual cooling and
annealing. Bonding in them is predominantly
metallic
Metallic may be a reference to:
*Metal
* Metalloid, metal-like substance
*Metallic bonding, type of chemical bonding
* Metallicity, in astronomy the proportion of elements other than helium and hydrogen in an object
*Metallic color, a color that ...
and the crystal structure primarily depends on efficiency of packing.
There are few compounds with lower oxidation states. A few
aluminium(I) In chemistry, aluminium(I) refers to monovalent aluminium (+1 oxidation state) in both ionic and covalent bonds. Along with aluminium(II), it is an extremely unstable form of aluminium.
While late Group 13 elements such as thallium and indium pr ...
compounds exist: AlF, AlCl, AlBr, and AlI exist in the gaseous phase when the respective trihalide is heated with aluminium, and at cryogenic temperatures. A stable derivative of aluminium monoiodide is the cyclic
adduct
An adduct (from the Latin ''adductus'', "drawn toward" alternatively, a contraction of "addition product") is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all co ...
formed with
triethylamine
Triethylamine is the chemical compound with the formula N(CH2CH3)3, commonly abbreviated Et3N. It is also abbreviated TEA, yet this abbreviation must be used carefully to avoid confusion with triethanolamine or tetraethylammonium, for which TEA ...
, Al
4I
4(NEt
3)
4. Al
2O and Al
2S also exist but are very unstable.
Very simple aluminium(II) compounds are invoked or observed in the reactions of Al metal with oxidants. For example,
aluminium monoxide
Aluminium(II) oxide or aluminium monoxide is a compound of aluminium and oxygen with the chemical formula AlO. It has been detected in the gas phase after explosion of aluminized grenades in the upper atmosphere and in stellar absorption spectra. ...
, AlO, has been detected in the gas phase after explosion and in stellar absorption spectra. More thoroughly investigated are compounds of the formula R
4Al
2 which contain an Al–Al bond and where R is a large organic
ligand
In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's electr ...
.
Organoaluminium compounds and related hydrides
![Trimethylaluminium-from-xtal-3D-bs-17-25](https://upload.wikimedia.org/wikipedia/commons/2/27/Trimethylaluminium-from-xtal-3D-bs-17-25.png)
A variety of compounds of empirical formula AlR
3 and AlR
1.5Cl
1.5 exist. The aluminium trialkyls and triaryls are reactive, volatile, and colorless liquids or low-melting solids. They catch fire spontaneously in air and react with water, thus necessitating precautions when handling them. They often form dimers, unlike their boron analogues, but this tendency diminishes for branched-chain alkyls (e.g.
Pr''i'',
Bu''i'', Me
3CCH
2); for example,
triisobutylaluminium
Triisobutylaluminium (TiBA) is an organoaluminium compound with the formula Al(CH2CH(CH3)2)3. This colorless pyrophoric liquid is mainly used to make linear primary alcohols and α-olefins.Michael J. Krause, Frank Orlandi, Alfred T. Saurage, Jos ...
exists as an equilibrium mixture of the monomer and dimer. These dimers, such as
trimethylaluminium
Trimethylaluminium is one of the simplest examples of an organoaluminium compound. Despite its name it has the formula Al2( CH3)6 (abbreviated as Al2Me6 or TMA), as it exists as a dimer. This colorless liquid is pyrophoric. It is an industriall ...
(Al
2Me
6), usually feature tetrahedral Al centers formed by dimerization with some alkyl group bridging between both aluminium atoms. They are
hard acids and react readily with ligands, forming adducts. In industry, they are mostly used in alkene insertion reactions, as discovered by
Karl Ziegler
Karl Waldemar Ziegler (26 November 1898 – 12 August 1973) was a German chemist who won the Nobel Prize in Chemistry in 1963, with Giulio Natta, for work on polymers. The Nobel Committee recognized his "excellent work on organometallic compounds ...
, most importantly in "growth reactions" that form long-chain unbranched primary alkenes and alcohols, and in the low-pressure polymerization of
ethene
Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon-carbon double bonds).
Ethylene is ...
and
propene
Propylene, also known as propene, is an unsaturated organic compound with the chemical formula CH3CH=CH2. It has one double bond, and is the second simplest member of the alkene class of hydrocarbons. It is a colorless gas with a faint petrole ...
. There are also some
heterocyclic
A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). Heterocyclic chemistry is the branch of organic chemistry dealing with the synthesis, properties, and ...
and cluster organoaluminium compounds involving Al–N bonds.
The industrially most important aluminium hydride is
lithium aluminium hydride
Lithium aluminium hydride, commonly abbreviated to LAH, is an inorganic compound with the chemical formula Li Al H4. It is a white solid, discovered by Finholt, Bond and Schlesinger in 1947. This compound is used as a reducing agent in organic ...
(LiAlH
4), which is used in as a reducing agent in
organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clayden, J.; ...
. It can be produced from
lithium hydride
Lithium hydride is an inorganic compound with the formula Li H. This alkali metal hydride is a colorless solid, although commercial samples are grey. Characteristic of a salt-like (ionic) hydride, it has a high melting point, and it is not solub ...
and
aluminium trichloride
Aluminium chloride, also known as aluminium trichloride, is an inorganic compound with the formula . It forms hexahydrate with the formula , containing six water molecules of hydration. Both are colourless crystals, but samples are often contam ...
. The simplest hydride,
aluminium hydride
Aluminium hydride (also known as alane and alumane) is an inorganic compound with the formula Al H3. Alane and its derivatives are common reducing (hydride addition) reagents in organic synthesis that are used in solution at both laboratory ...
or alane, is not as important. It is a polymer with the formula (AlH
3)
''n'', in contrast to the corresponding boron hydride that is a dimer with the formula (BH
3)
2.
Natural occurrence
Space
Aluminium'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 3.15
ppm (parts per million).
[
] It is the twelfth most abundant of all elements and third most abundant among the elements that have odd atomic numbers, after hydrogen and nitrogen.
The only stable isotope of aluminium,
27Al, is the eighteenth most abundant nucleus in the Universe. It is created almost entirely after fusion of carbon in massive stars that will later become
Type II supernova
A Type II supernova (plural: ''supernovae'' or ''supernovas'') results from the rapid collapse and violent explosion of a massive star. A star must have at least 8 times, but no more than 40 to 50 times, the mass of the Sun () to undergo this ...
s: this fusion creates
26Mg, which, upon capturing free protons and neutrons becomes aluminium. Some smaller quantities of
27Al are created in
hydrogen burning
Stellar nucleosynthesis is the creation (nucleosynthesis) of chemical elements by nuclear fusion reactions within stars. Stellar nucleosynthesis has occurred since the original creation of hydrogen, helium and lithium during the Big Bang. As a ...
shells of evolved stars, where
26Mg can capture free protons.
Essentially all aluminium now in existence is
27Al.
26Al was present in the early Solar System with abundance of 0.005% relative to
27Al but its half-life of 728,000 years is too short for any original nuclei to survive;
26Al is therefore
extinct
Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
.
Unlike for
27Al, hydrogen burning is the primary source of
26Al, with the nuclide emerging after a nucleus of
25Mg catches a free proton. However, the
trace quantities of
26Al that do exist are the most common
gamma ray
A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically ...
emitter in the
interstellar gas
In astronomy, the interstellar medium is the matter and radiation that exist in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstella ...
;
if the original
26Al were still present,
gamma ray maps of the Milky Way would be brighter.
Earth
![Bauxite hérault](https://upload.wikimedia.org/wikipedia/commons/1/11/Bauxite_h%C3%A9rault.JPG)
Overall, the Earth is about 1.59% aluminium by mass (seventh in abundance by mass).
[William F McDonoug]
The composition of the Earth
quake.mit.edu, archived by the Internet Archive Wayback Machine. Aluminium occurs in greater proportion in the Earth's crust than in the Universe at large, because aluminium easily forms the oxide and becomes bound into rocks and stays in the
Earth's crust
Earth's crust is Earth's thin outer shell of rock, referring to less than 1% of Earth's radius and volume. It is the top component of the lithosphere, a division of Earth's layers that includes the crust and the upper part of the mantle. The ...
, while less reactive metals sink to the core.
In the Earth's crust, aluminium is the most abundant metallic element (8.23% by mass
) and the third most abundant of all elements (after oxygen and silicon). A large number of silicates in the Earth's crust contain aluminium.
In contrast, the Earth's
mantle is only 2.38% aluminium by mass. Aluminium also occurs in seawater at a concentration of 2 μg/kg.
Because of its strong affinity for oxygen, aluminium is almost never found in the elemental state; instead it is found in oxides or silicates.
Feldspar
Feldspars are a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagioclase'' (sodium-calcium) feldsp ...
s, the most common group of minerals in the Earth's crust, are aluminosilicates. Aluminium also occurs in the minerals
beryl
Beryl ( ) is a mineral composed of beryllium aluminium silicate with the chemical formula Be3Al2Si6O18. Well-known varieties of beryl include emerald and aquamarine. Naturally occurring, hexagonal crystals of beryl can be up to several mete ...
,
cryolite
Cryolite ( Na3 Al F6, sodium hexafluoroaluminate) is an uncommon mineral identified with the once-large deposit at Ivittuut on the west coast of Greenland, mined commercially until 1987.
History
Cryolite was first described in 1798 by Danish vete ...
,
garnet
Garnets () are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives.
All species of garnets possess similar physical properties and crystal forms, but differ in chemical composition. The different s ...
,
spinel
Spinel () is the magnesium/aluminium member of the larger spinel group of minerals. It has the formula in the cubic crystal system. Its name comes from the Latin word , which means ''spine'' in reference to its pointed crystals.
Properties
S ...
, and
turquoise
Turquoise is an opaque, blue-to-green mineral that is a hydrated phosphate of copper and aluminium, with the chemical formula . It is rare and valuable in finer grades and has been prized as a gemstone and ornamental stone for thousands of yea ...
. Impurities in Al
2O
3, such as
chromium
Chromium is a chemical element with the symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard, and brittle transition metal.
Chromium metal is valued for its high corrosion resistance and hardne ...
and
iron
Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...
, yield the
gemstone
A gemstone (also called a fine gem, jewel, precious stone, or semiprecious stone) is a piece of mineral crystal which, in cut and polished form, is used to make jewelry or other adornments. However, certain rocks (such as lapis lazuli, opal, ...
s
ruby
A ruby is a pinkish red to blood-red colored gemstone, a variety of the mineral corundum ( aluminium oxide). Ruby is one of the most popular traditional jewelry gems and is very durable. Other varieties of gem-quality corundum are called sa ...
and
sapphire
Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide () with trace amounts of elements such as iron, titanium, chromium, vanadium, or magnesium. The name sapphire is derived via the Latin "sapphir ...
, respectively.
Native aluminium metal is extremely rare and can only be found as a minor phase in low oxygen
fugacity
In chemical thermodynamics, the fugacity of a real gas is an effective partial pressure which replaces the mechanical partial pressure in an accurate computation of the chemical equilibrium constant. It is equal to the pressure of an ideal gas whic ...
environments, such as the interiors of certain volcanoes. Native aluminium has been reported in
cold seep
A cold seep (sometimes called a cold vent) is an area of the ocean floor where hydrogen sulfide, methane and other hydrocarbon-rich fluid seepage occurs, often in the form of a brine pool. ''Cold'' does not mean that the temperature of the see ...
s in the northeastern
continental slope
A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. The continental margin ...
of the
South China Sea
The South China Sea is a marginal sea of the Western Pacific Ocean. It is bounded in the north by the shores of South China (hence the name), in the west by the Indochinese Peninsula, in the east by the islands of Taiwan and northwestern Phil ...
. It is possible that these deposits resulted from
bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
l
reduction of tetrahydroxoaluminate Al(OH)
4−.
Although aluminium is a common and widespread element, not all aluminium minerals are economically viable sources of the metal. Almost all metallic aluminium is produced from the
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 Apr ...
bauxite
Bauxite is a sedimentary rock with a relatively high aluminium content. It is the world's main source of aluminium and gallium. Bauxite consists mostly of the aluminium minerals gibbsite (Al(OH)3), boehmite (γ-AlO(OH)) and diaspore (α-AlO(O ...
(AlO
''x''(OH)
3–2''x''). Bauxite occurs as a
weathering
Weathering is the deterioration of rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little or no movement), ...
product of low iron and silica bedrock in tropical climatic conditions. In 2017, most bauxite was mined in Australia, China, Guinea, and India.
History
![Friedrich_W%C3%B6hler_Litho](https://upload.wikimedia.org/wikipedia/commons/3/32/Friedrich_W%C3%B6hler_Litho.jpg)
The history of aluminium has been shaped by usage of
alum
An alum () is a type of chemical compound, usually a hydrated double salt, double sulfate salt (chemistry), salt of aluminium with the general chemical formula, formula , where is a valence (chemistry), monovalent cation such as potassium or a ...
. The first written record of alum, made by
Greek
Greek may refer to:
Greece
Anything of, from, or related to Greece, a country in Southern Europe:
*Greeks, an ethnic group.
*Greek language, a branch of the Indo-European language family.
**Proto-Greek language, the assumed last common ancestor ...
historian
Herodotus
Herodotus ( ; grc, , }; BC) was an ancient Greek historian and geographer from the Greek city of Halicarnassus, part of the Persian Empire (now Bodrum, Turkey) and a later citizen of Thurii in modern Calabria ( Italy). He is known f ...
, dates back to the 5th century BCE. The ancients are known to have used alum as a dyeing
mordant
A mordant or dye fixative is a substance used to set (i.e. bind) dyes on fabrics by forming a coordination complex with the dye, which then attaches to the fabric (or tissue). It may be used for dyeing fabrics or for intensifying stains in ...
and for city defense. After the
Crusades
The Crusades were a series of religious wars initiated, supported, and sometimes directed by the Latin Church in the medieval period. The best known of these Crusades are those to the Holy Land in the period between 1095 and 1291 that were in ...
, alum, an indispensable good in the European fabric industry,
was a subject of international commerce; it was imported to Europe from the eastern Mediterranean until the mid-15th century.
The nature of alum remained unknown. Around 1530, Swiss physician
Paracelsus
Paracelsus (; ; 1493 – 24 September 1541), born Theophrastus von Hohenheim (full name Philippus Aureolus Theophrastus Bombastus von Hohenheim), was a Swiss physician, alchemist, lay theologian, and philosopher of the German Renaissance.
He w ...
suggested alum was a salt of an earth of alum. In 1595, German doctor and chemist
Andreas Libavius
Andreas Libavius or Andrew Libavius was born in Halle, Germany c. 1550 and died in July 1616. Libavius was a renaissance man who spent time as a professor at the University of Jena teaching history and poetry. After which he became a physician a ...
experimentally confirmed this.
In 1722, German chemist
Friedrich Hoffmann
Friedrich Hoffmann or Hofmann (19 February 1660 – 12 November 1742) was a German physician and chemist. He is also sometimes known in English as Frederick Hoffmann.
Life
His family had been connected with medicine for 200 years before him. Bo ...
announced his belief that the base of alum was a distinct earth. In 1754, German chemist
Andreas Sigismund Marggraf
Andreas Sigismund Marggraf (; 3 March 1709 – 7 August 1782) was a German chemist from Berlin, then capital of the Margraviate of Brandenburg, and a pioneer of analytical chemistry. He isolated zinc in 1746 by heating Calamine (mineral), calamine ...
synthesized alumina by boiling clay in sulfuric acid and subsequently adding
potash
Potash () includes various mined and manufactured salts that contain potassium in water-soluble form. .
Attempts to produce aluminium metal date back to 1760. The first successful attempt, however, was completed in 1824 by Danish physicist and chemist
Hans Christian Ørsted
Hans Christian Ørsted ( , ; often rendered Oersted in English; 14 August 17779 March 1851) was a Danish physicist and chemist who discovered that electric currents create magnetic fields, which was the first connection found between electricity ...
. He reacted anhydrous
aluminium chloride
Aluminium chloride, also known as aluminium trichloride, is an inorganic compound with the formula . It forms hexahydrate with the formula , containing six water molecules of hydration. Both are colourless crystals, but samples are often contam ...
with potassium
amalgam
Amalgam most commonly refers to:
* Amalgam (chemistry), mercury alloy
* Amalgam (dentistry), material of silver tooth fillings
** Bonded amalgam, used in dentistry
Amalgam may also refer to:
* Amalgam Comics, a publisher
* Amalgam Digital
...
, yielding a lump of metal looking similar to tin.
He presented his results and demonstrated a sample of the new metal in 1825.
In 1827, German chemist
Friedrich Wöhler
Friedrich Wöhler () FRS(For) HonFRSE (31 July 180023 September 1882) was a German chemist known for his work in inorganic chemistry, being the first to isolate the chemical elements beryllium and yttrium in pure metallic form. He was the firs ...
repeated Ørsted's experiments but did not identify any aluminium.
(The reason for this inconsistency was only discovered in 1921.) He conducted a similar experiment in the same year by mixing anhydrous aluminium chloride with potassium and produced a powder of aluminium.
In 1845, he was able to produce small pieces of the metal and described some physical properties of this metal. For many years thereafter, Wöhler was credited as the discoverer of aluminium.
![Eros-piccadilly-circus](https://upload.wikimedia.org/wikipedia/commons/7/78/Eros-piccadilly-circus.jpg)
As Wöhler's method could not yield great quantities of aluminium, the metal remained rare; its cost exceeded that of gold.
The first industrial production of aluminium was established in 1856 by French chemist
Henri Etienne Sainte-Claire Deville
Henri is an Estonian, Finnish, French, German and Luxembourgish form of the masculine given name Henry.
People with this given name
; French noblemen
:'' See the 'List of rulers named Henry' for Kings of France named Henri.''
* Henri I de Montm ...
and companions. Deville had discovered that aluminium trichloride could be reduced by sodium, which was more convenient and less expensive than potassium, which Wöhler had used. Even then, aluminium was still not of great purity and produced aluminium differed in properties by sample. Because of its electricity-conducting capacity, aluminium was used as the cap of the
Washington Monument
The Washington Monument is an obelisk shaped building within the National Mall in Washington, D.C., built to commemorate George Washington, once commander-in-chief of the Continental Army (1775–1784) in the American Revolutionary War and the ...
, completed in 1885. The tallest building in the world at the time, the non-corroding metal cap was intended to serve as a
lightning rod
A lightning rod or lightning conductor (British English) is a metal rod mounted on a structure and intended to protect the structure from a lightning strike. If lightning hits the structure, it will preferentially strike the rod and be conducte ...
peak.
The first industrial large-scale production method was independently developed in 1886 by French engineer
Paul Héroult
Paul (Louis-Toussaint) Héroult (10 April 1863 – 9 May 1914) was a French scientist. He was the inventor of the aluminium electrolysis and developed the first successful commercial electric arc furnace. He lived in Thury-Harcourt, Normandy.
...
and American engineer
Charles Martin Hall
Charles Martin Hall (December 6, 1863 – December 27, 1914) was an American inventor, businessman, and chemist. He is best known for his invention in 1886 of an inexpensive method for producing aluminum, which became the first metal to atta ...
; it is now known as the
Hall–Héroult process
The Hall–Héroult process is the major industrial process for smelting aluminium. It involves dissolving aluminium oxide (alumina) (obtained most often from bauxite, aluminium's chief ore, through the Bayer process) in molten cryolite, and el ...
. The Hall–Héroult process converts alumina into metal. Austrian chemist
Carl Joseph Bayer discovered a way of purifying bauxite to yield alumina, now known as the
Bayer process
The Bayer process is the principal industrial means of refining bauxite to produce alumina (aluminium oxide) and was developed by Carl Josef Bayer. Bauxite, the most important ore of aluminium, contains only 30–60% aluminium oxide (Al2O3), the ...
, in 1889. Modern production of the aluminium metal is based on the Bayer and Hall–Héroult processes.
Prices of aluminium dropped and aluminium became widely used in jewelry, everyday items, eyeglass frames, optical instruments, tableware, and
foil
Foil may refer to:
Materials
* Foil (metal), a quite thin sheet of metal, usually manufactured with a rolling mill machine
* Metal leaf, a very thin sheet of decorative metal
* Aluminium foil, a type of wrapping for food
* Tin foil, metal foil ...
in the 1890s and early 20th century. Aluminium's ability to form hard yet light alloys with other metals provided the metal with many uses at the time. During
World War I
World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...
, major governments demanded large shipments of aluminium for light strong airframes; during
World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
, demand by major governments for aviation was even higher.
By the mid-20th century, aluminium had become a part of everyday life and an essential component of housewares. In 1954, production of aluminium surpassed that of
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
, historically second in production only to iron, making it the most produced
non-ferrous metal
In metallurgy, non-ferrous metals are metals or alloys that do not contain iron (allotropes of iron, ferrite, and so on) in appreciable amounts.
Generally more costly than ferrous metals, non-ferrous metals are used because of desirable proper ...
. During the mid-20th century, aluminium emerged as a civil engineering material, with building applications in both basic construction and interior finish work, and increasingly being used in military engineering, for both airplanes and land armor vehicle engines.
Earth's first artificial satellite, launched in 1957, consisted of two separate aluminium semi-spheres joined and all subsequent space vehicles have used aluminium to some extent.
The
aluminium can
An Aluminum can (British English: Tin can) is a single-use container for packaging made primarily of aluminum.
It is commonly used for food and beverages such as milk and soup but also for products such as oil, chemicals, and other liquids. Globa ...
was invented in 1956 and employed as a storage for drinks in 1958.
![Aluminium - world production trend](https://upload.wikimedia.org/wikipedia/commons/9/96/Aluminium_-_world_production_trend.svg)
Throughout the 20th century, the production of aluminium rose rapidly: while the world production of aluminium in 1900 was 6,800 metric tons, the annual production first exceeded 100,000 metric tons in 1916; 1,000,000 tons in 1941; 10,000,000 tons in 1971.
In the 1970s, the increased demand for aluminium made it an exchange commodity; it entered the
London Metal Exchange
The London Metal Exchange (LME) is a futures and forwards exchange with the world's largest market in standarised forward contracts, futures contracts and options on base metals. The exchange also offers contracts on ferrous metals and precious ...
, the oldest industrial metal exchange in the world, in 1978.
The output continued to grow: the annual production of aluminium exceeded 50,000,000 metric tons in 2013.
The
real price
In economics, nominal value is measured in terms of money, whereas real value is measured against goods or services. A real value is one which has been adjusted for inflation, enabling comparison of quantities as if the prices of goods had not c ...
for aluminium declined from $14,000 per metric ton in 1900 to $2,340 in 1948 (in 1998 United States dollars).
Extraction and processing costs were lowered over technological progress and the scale of the economies. However, the need to exploit lower-grade poorer quality deposits and the use of fast increasing input costs (above all, energy) increased the net cost of aluminium; the real price began to grow in the 1970s with the rise of energy cost. Production moved from the industrialized countries to countries where production was cheaper. Production costs in the late 20th century changed because of advances in technology, lower energy prices, exchange rates of the United States dollar, and alumina prices. The
BRIC
BRIC is a grouping acronym referring to the developing countries of Brazil, Russia, India, and China, which are identified as rising economic powers. It is typically rendered as "the BRIC," "the BRIC countries," "the BRIC economies," or alte ...
countries' combined share in primary production and primary consumption grew substantially in the first decade of the 21st century. China is accumulating an especially large share of the world's production thanks to an abundance of resources, cheap energy, and governmental stimuli; it also increased its consumption share from 2% in 1972 to 40% in 2010. In the United States, Western Europe, and Japan, most aluminium was consumed in transportation, engineering, construction, and packaging. In 2021, prices for industrial metals such as aluminium have soared to near-record levels as
energy shortages in China drive up costs for electricity.
Etymology
The names ''aluminium'' and ''aluminum'' are derived from the word ''alumine'', an obsolete term for ''alumina'', a
naturally occurring oxide of aluminium.
[
] ''Alumine'' was borrowed from French, which in turn derived it from ''alumen'', the classical Latin name for
alum
An alum () is a type of chemical compound, usually a hydrated double salt, double sulfate salt (chemistry), salt of aluminium with the general chemical formula, formula , where is a valence (chemistry), monovalent cation such as potassium or a ...
, the mineral from which it was collected.
[
] The Latin word ''alumen'' stems from the
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 ...
root ''*alu-'' meaning "bitter" or "beer".
Origins
British chemist
Humphry Davy
Sir Humphry Davy, 1st Baronet, (17 December 177829 May 1829) was a British chemist and inventor who invented the Davy lamp and a very early form of arc lamp. He is also remembered for isolating, by using electricity, several elements for t ...
, who performed a number of experiments aimed to isolate the metal, is credited as the person who named the element. The first name proposed for the metal to be isolated from alum was ''alumium'', which Davy suggested in an 1808 article on his electrochemical research, published in
Philosophical Transactions of the Royal Society
''Philosophical Transactions of the Royal Society'' is a scientific journal published by the Royal Society. In its earliest days, it was a private venture of the Royal Society's secretary. It was established in 1665, making it the first journa ...
.
It appeared that the name was created from the English word ''alum'' and the Latin suffix ''-ium''; but it was customary then to give elements names originating in Latin, so that this name was not adopted universally. This name was criticized by contemporary chemists from France, Germany, and Sweden, who insisted the metal should be named for the oxide, alumina, from which it would be isolated. The English name ''alum'' does not come directly from Latin, whereas ''alumine''/''alumina'' obviously comes from the Latin word ''alumen'' (upon
declension
In linguistics, declension (verb: ''to decline'') is the changing of the form of a word, generally to express its syntactic function in the sentence, by way of some inflection. Declensions may apply to nouns, pronouns, adjectives, adverbs, and ar ...
, ''alumen'' changes to ''alumin-'').
One example was ''Essai sur la Nomenclature chimique'' (July 1811), written in French by a Swedish chemist,
Jöns Jacob Berzelius
Baron Jöns Jacob Berzelius (; by himself and his contemporaries named only Jacob Berzelius, 20 August 1779 – 7 August 1848) was a Swedish chemist. Berzelius is considered, along with Robert Boyle, John Dalton, and Antoine Lavoisier, to be on ...
, in which the name ''aluminium'' is given to the element that would be synthesized from alum.
[.] (Another article in the same journal issue also gives the name ''aluminium'' to the metal whose oxide is the basis of
sapphire
Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide () with trace amounts of elements such as iron, titanium, chromium, vanadium, or magnesium. The name sapphire is derived via the Latin "sapphir ...
.) A January 1811 summary of one of Davy's lectures at the
Royal Society
The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, re ...
mentioned the name ''aluminium'' as a possibility. The next year, Davy published a chemistry textbook in which he used the spelling ''aluminum''.
Both spellings have coexisted since. Their usage is regional: ''aluminum'' dominates in the United States and Canada; ''aluminium'', in the rest of the English-speaking world.
[
]
Spelling
In 1812, a British scientist,
Thomas Young, wrote an anonymous review of Davy's book, in which he proposed the name ''aluminium'' instead of ''aluminum'', which he thought had a "less classical sound". This name did catch on: although the ' spelling was occasionally used in Britain, the American scientific language used ' from the start.
Most scientists throughout the world used ' in the 19th century;
and it was entrenched in many other European languages, such as
French,
German
German(s) may refer to:
* Germany (of or related to)
** Germania (historical use)
* Germans, citizens of Germany, people of German ancestry, or native speakers of the German language
** For citizens of Germany, see also German nationality law
**Ge ...
, and
Dutch
Dutch commonly refers to:
* Something of, from, or related to the Netherlands
* Dutch people ()
* Dutch language ()
Dutch may also refer to:
Places
* Dutch, West Virginia, a community in the United States
* Pennsylvania Dutch Country
People E ...
. In 1828, an American lexicographer,
Noah Webster
Noah ''Nukh''; am, ኖህ, ''Noḥ''; ar, نُوح '; grc, Νῶε ''Nôe'' () is the tenth and last of the pre-Flood patriarchs in the traditions of Abrahamic religions. His story appears in the Hebrew Bible (Book of Genesis, chapters 5– ...
, entered only the ''aluminum'' spelling in his ''
American Dictionary of the English Language
''Webster's Dictionary'' is any of the English language dictionaries edited in the early 19th century by American lexicographer Noah Webster (1758–1843), as well as numerous related or unrelated dictionaries that have adopted the Webster's n ...
''. In the 1830s, the ' spelling gained usage in the United States; by the 1860s, it had become the more common spelling there outside science.
In 1892, Hall used the ' spelling in his advertising handbill for his new electrolytic method of producing the metal, despite his constant use of the ' spelling in all the patents he filed between 1886 and 1903: it is unknown whether this spelling was introduced by mistake or intentionally; but Hall preferred ''aluminum'' since its introduction because it resembled ''
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 ...
'', the name of a prestigious metal. By 1890, both spellings had been common in the United States, the ' spelling being slightly more common; by 1895, the situation had reversed; by 1900, ''aluminum'' had become twice as common as ''aluminium''; in the next decade, the ' spelling dominated American usage. In 1925, the
American Chemical Society
The American Chemical Society (ACS) is a scientific society based in the United States that supports scientific inquiry in the field of chemistry. Founded in 1876 at New York University, the ACS currently has more than 155,000 members at all d ...
adopted this spelling.
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 working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is ...
(IUPAC) adopted ''aluminium'' as the standard international name for the element in 1990.
In 1993, they recognized ''aluminum'' as an acceptable variant;
the most recent IUPAC nomenclature of inorganic chemistry 2005, 2005 edition of the IUPAC nomenclature of inorganic chemistry also acknowledges this spelling. IUPAC official publications use the ' spelling as primary, and they list both where it is appropriate.
Production and refinement
The production of aluminium starts with the extraction of
bauxite
Bauxite is a sedimentary rock with a relatively high aluminium content. It is the world's main source of aluminium and gallium. Bauxite consists mostly of the aluminium minerals gibbsite (Al(OH)3), boehmite (γ-AlO(OH)) and diaspore (α-AlO(O ...
rock from the ground. The bauxite is processed and transformed using the
Bayer process
The Bayer process is the principal industrial means of refining bauxite to produce alumina (aluminium oxide) and was developed by Carl Josef Bayer. Bauxite, the most important ore of aluminium, contains only 30–60% aluminium oxide (Al2O3), the ...
into
alumina, which is then processed using the
Hall–Héroult process
The Hall–Héroult process is the major industrial process for smelting aluminium. It involves dissolving aluminium oxide (alumina) (obtained most often from bauxite, aluminium's chief ore, through the Bayer process) in molten cryolite, and el ...
, resulting in the final aluminium metal.
Aluminium production is highly energy-consuming, and so the producers tend to locate smelters in places where electric power is both plentiful and inexpensive.
As of 2019, the world's largest Smelting, smelters of aluminium are located in China, India, Russia, Canada, and the United Arab Emirates,
while China is by far the top producer of aluminium with a world share of fifty-five percent.
According to the International Resource Panel's Metal Stocks in Society report, the global per capita stock of aluminium in use in society (i.e. in cars, buildings, electronics, etc.) is . Much of this is in more-developed countries ( per capita) rather than less-developed countries ( per capita).
Bayer process
Bauxite is converted to alumina by the Bayer process. Bauxite is blended for uniform composition and then is ground. The resulting slurry is mixed with a hot solution of
sodium hydroxide
Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations and hydroxide anions .
Sodium hydroxide is a highly caustic base and alkali ...
; the mixture is then treated in a digester vessel at a pressure well above atmospheric, dissolving the aluminium hydroxide in bauxite while converting impurities into relatively insoluble compounds:
After this reaction, the slurry is at a temperature above its atmospheric boiling point. It is cooled by removing steam as pressure is reduced. The bauxite residue is separated from the solution and discarded. The solution, free of solids, is seeded with small crystals of aluminium hydroxide; this causes decomposition of the [Al(OH)
4]
− ions to aluminium hydroxide. After about half of aluminium has precipitated, the mixture is sent to classifiers. Small crystals of aluminium hydroxide are collected to serve as seeding agents; coarse particles are converted to alumina by heating; the excess solution is removed by evaporation, (if needed) purified, and recycled.
Hall–Héroult process
![Tovarna glinice in aluminija Kidričevo - kupi aluminija 1968](https://upload.wikimedia.org/wikipedia/commons/e/e8/Tovarna_glinice_in_aluminija_Kidri%C4%8Devo_-_kupi_aluminija_1968.jpg)
The conversion of
alumina to aluminium metal is achieved by the
Hall–Héroult process
The Hall–Héroult process is the major industrial process for smelting aluminium. It involves dissolving aluminium oxide (alumina) (obtained most often from bauxite, aluminium's chief ore, through the Bayer process) in molten cryolite, and el ...
. In this energy-intensive process, a solution of alumina in a molten () mixture of
cryolite
Cryolite ( Na3 Al F6, sodium hexafluoroaluminate) is an uncommon mineral identified with the once-large deposit at Ivittuut on the west coast of Greenland, mined commercially until 1987.
History
Cryolite was first described in 1798 by Danish vete ...
(Na
3AlF
6) with calcium fluoride is electrolysis, electrolyzed to produce metallic aluminium. The liquid aluminium metal sinks to the bottom of the solution and is tapped off, and usually cast into large blocks called Bar stock, aluminium billets for further processing.
Anodes of the electrolysis cell are made of carbon—the most resistant material against fluoride corrosion—and either bake at the process or are prebaked. The former, also called Söderberg anodes, are less power-efficient and fumes released during baking are costly to collect, which is why they are being replaced by prebaked anodes even though they save the power, energy, and labor to prebake the cathodes. Carbon for anodes should be preferably pure so that neither aluminium nor the electrolyte is contaminated with ash. Despite carbon's resistivity against corrosion, it is still consumed at a rate of 0.4–0.5 kg per each kilogram of produced aluminium. Cathodes are made of anthracite; high purity for them is not required because impurities Leaching (chemistry), leach only very slowly. The cathode is consumed at a rate of 0.02–0.04 kg per each kilogram of produced aluminium. A cell is usually terminated after 2–6 years following a failure of the cathode.
The Hall–Heroult process produces aluminium with a purity of above 99%. Further purification can be done by the Hoopes process. This process involves the electrolysis of molten aluminium with a sodium, barium, and aluminium fluoride electrolyte. The resulting aluminium has a purity of 99.99%.
Electric power represents about 20 to 40% of the cost of producing aluminium, depending on the location of the smelter. Aluminium production consumes roughly 5% of electricity generated in the United States.
Because of this, alternatives to the Hall–Héroult process have been researched, but none has turned out to be economically feasible.
Recycling
![Waste bins recyclable](https://upload.wikimedia.org/wikipedia/commons/a/a3/Waste_bins_recyclable.jpg)
Recovery of the metal through recycling has become an important task of the aluminium industry. Recycling was a low-profile activity until the late 1960s, when the growing use of aluminium beverage cans brought it to public awareness. Recycling involves melting the scrap, a process that requires only 5% of the energy used to produce aluminium from ore, though a significant part (up to 15% of the input material) is lost as dross (ash-like oxide). An aluminium stack melter produces significantly less dross, with values reported below 1%.
White dross from primary aluminium production and from secondary recycling operations still contains useful quantities of aluminium that can be Aluminium dross recycling, extracted industrially. The process produces aluminium billets, together with a highly complex waste material. This waste is difficult to manage. It reacts with water, releasing a mixture of gases (including, among others, hydrogen,
acetylene
Acetylene (systematic name: ethyne) is the chemical compound with the formula and structure . It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in its pure ...
, and ammonia), which spontaneously ignites on contact with air; contact with damp air results in the release of copious quantities of ammonia gas. Despite these difficulties, the waste is used as a filler in asphalt and concrete.
Applications
Metal
The global production of aluminium in 2016 was 58.8 million metric tons. It exceeded that of any other metal except
iron
Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...
(1,231 million metric tons).
Aluminium is almost always alloyed, which markedly improves its mechanical properties, especially when tempering (metallurgy), tempered. For example, the common aluminium foils and beverage cans are alloys of 92% to 99% aluminium. The main alloying agents are
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
, zinc,
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 ...
, manganese, 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 ...
(e.g., duralumin) with the levels of other metals in a few percent by weight. Aluminium, both wrought and cast, has been alloyed with: manganese,
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 ...
,
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 ...
,
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
and zinc among others.
For example, the Kynal family of alloys was developed by the British chemical manufacturer Imperial Chemical Industries.
![Drinking can ring-pull tab](https://upload.wikimedia.org/wikipedia/commons/f/ff/Drinking_can_ring-pull_tab.jpg)
The major uses for aluminium metal are in:
* Transportation (automobiles, aircraft, trucks, railway cars, marine vessels, bicycles, spacecraft, ''etc.''). Aluminium is used because of its low density;
* Packaging (aluminium can, cans, foil, frame, ''etc.''). Aluminium is used because it is non-toxic (see #Toxicity, below), non-Adsorption, adsorptive, and splinter-proof;
* Building and construction (windows, doors, Siding (construction), siding, building wire, sheathing, roofing, ''etc.''). Since steel is cheaper, aluminium is used when lightness, corrosion resistance, or engineering features are important;
* Electricity-related uses (conductor alloys, motors, and generators, transformers, capacitors, ''etc.''). Aluminium is used because it is relatively cheap, highly conductive, has adequate mechanical strength and low density, and resists corrosion;
* A wide range of household items, from cooking utensils to furniture. Low density, good appearance, ease of fabrication, and durability are the key factors of aluminium usage;
* Machinery and equipment (processing equipment, pipes, tools). Aluminium is used because of its corrosion resistance, non-pyrophoricity, and mechanical strength.
* Portable computer cases. Currently rarely used without alloying, but aluminium can be recycled and clean aluminium has residual market value: for example, the Used Beverage Can, used beverage can (UBC) material was used to encase the electronic components of MacBook Air laptop, Pixel 5 smartphone or Montblanc (company), Summit Lite smartwatch.
[
]
Compounds
The great majority (about 90%) of
aluminium oxide is converted to metallic aluminium.
Being a very hard material (
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 ...
9),
alumina is widely used as an abrasive;
being extraordinarily chemically inert, it is useful in highly reactive environments such as high pressure sodium lamps.
Aluminium oxide is commonly used as a catalyst for industrial processes;
e.g. the Claus process to convert
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 ...
to sulfur in refineries and to alkylation, alkylate amines.
Many industrial Catalysis, catalysts are catalyst support, supported by alumina, meaning that the expensive Catalysis, catalyst material is dispersed over a surface of the inert alumina.
Another principal use is as a drying agent or absorbent.
![Pulsed Laser Deposition in Action](https://upload.wikimedia.org/wikipedia/commons/0/03/Pulsed_Laser_Deposition_in_Action.jpg)
Several sulfates of aluminium have industrial and commercial application. Aluminium sulfate (in its hydrate form) is produced on the annual scale of several millions of metric tons.
About two-thirds is consumed in water treatment.
The next major application is in the manufacture of paper.
It is also used as a mordant in dyeing, in pickling seeds, deodorizing of mineral oils, in Tanning (leather), leather tanning, and in production of other aluminium compounds.
Two kinds of alum, ammonium alum and potassium alum, were formerly used as mordants and in leather tanning, but their use has significantly declined following availability of high-purity aluminium sulfate.
Anhydrous
aluminium chloride
Aluminium chloride, also known as aluminium trichloride, is an inorganic compound with the formula . It forms hexahydrate with the formula , containing six water molecules of hydration. Both are colourless crystals, but samples are often contam ...
is used as a catalyst in chemical and petrochemical industries, the dyeing industry, and in synthesis of various inorganic and organic compounds.
Aluminium hydroxychlorides are used in purifying water, in the paper industry, and as antiperspirants.
Sodium aluminate is used in treating water and as an accelerator of solidification of cement.
Many aluminium compounds have niche applications, for example:
* Aluminium acetate in solution is used as an astringent.
* Aluminium phosphate is used in the manufacture of glass, ceramic, Wood pulp, pulp and paper products, cosmetics, paints, varnishes, and in dental cement.
* Aluminium hydroxide is used as an antacid, and mordant; it is used also in water purification, the manufacture of glass and ceramics, and in the waterproofing of Textile, fabrics.
* Lithium aluminium hydride is a powerful reducing agent used in
organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clayden, J.; ...
.
* Organoaluminium chemistry, Organoaluminiums are used as
Lewis acid
A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any sp ...
s and co-catalysts.
* Methylaluminoxane is a co-catalyst for Ziegler–Natta olefin polymerization to produce vinyl polymers such as polyethene.
* Aqueous aluminium ions (such as aqueous aluminium sulfate) are used to treat against fish parasites such as ''Gyrodactylus salaris''.
* In many vaccines, certain aluminium salts serve as an immune Immunologic adjuvant, adjuvant (immune response booster) to allow the protein in the vaccine to achieve sufficient potency as an immune stimulant.
Aluminized substrates
Aluminizing is the process of coating a structure or material with a thin layer of aluminium. It is done to impart specific traits that the underlying substrate (materials science), substrate lacks, such as a certain chemical or physical property. Aluminized materials include:
* Aluminized steel, for corrosion resistance and other properties
* Aluminized screen, for display devices
* Aluminized cloth, to reflect heat
* Aluminized mylar, to reflect heat
Biology
![Al absorption by skin](https://upload.wikimedia.org/wikipedia/commons/2/24/Al_absorption_by_skin.jpg)
Despite its widespread occurrence in the Earth's crust, aluminium has no known function in biology.
At pH 6–9 (relevant for most natural waters), aluminium precipitates out of water as the hydroxide and is hence not available; most elements behaving this way have no biological role or are toxic.
Aluminium sulfate has an Median lethal dose, LD
50 of 6207 mg/kg (oral, mouse), which corresponds to 435 grams for an person.
Toxicity
Aluminium is classified as a non-carcinogen by the United States Department of Health and Human Services.
A review published in 1988 said that there was little evidence that normal exposure to aluminium presents a risk to healthy adult,
and a 2014 multi-element toxicology review was unable to find deleterious effects of aluminium consumed in amounts not greater than 40 mg/day per kg of body weight, body mass.
Most aluminium consumed will leave the body in feces; most of the small part of it that enters the bloodstream, will be excreted via urine;
nevertheless some aluminium does pass the blood-brain barrier and is lodged preferentially in the brains of Alzheimer's patients.
[
] Evidence published in 1989 indicates that, for Alzheimer's patients, aluminium may act by electrostatically crosslinking proteins, thus down-regulating genes in the superior temporal gyrus.
Effects
Aluminium, although rarely, can cause vitamin D-resistant osteomalacia, erythropoietin-resistant microcytic anemia, and central nervous system alterations. People with kidney insufficiency are especially at a risk.
Chronic ingestion of hydrated aluminium silicates (for excess gastric acidity control) may result in aluminium binding to intestinal contents and increased elimination of other metals, such as
iron
Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...
or zinc; sufficiently high doses (>50 g/day) can cause anemia.
![Al transport across human cells](https://upload.wikimedia.org/wikipedia/commons/4/49/Al_transport_across_human_cells.jpg)
During the 1988 Camelford water pollution incident people in Camelford had their drinking water contaminated with aluminium sulfate for several weeks. A final report into the incident in 2013 concluded it was unlikely that this had caused long-term health problems.
Aluminium has been suspected of being a possible cause of Alzheimer's disease, but research into this for over 40 years has found, , no good evidence of causal effect.
Aluminium increases estrogen-related gene expression in human breast cancer cells cultured in the laboratory. In very high doses, aluminium is associated with altered function of the blood–brain barrier. A small percentage of people
have contact allergy, allergies to aluminium and experience itchy red rashes, headache, muscle pain, joint pain, poor memory, insomnia, depression, asthma, irritable bowel syndrome, or other symptoms upon contact with products containing aluminium.
Exposure to powdered aluminium or aluminium welding fumes can cause pulmonary fibrosis. Fine aluminium powder can ignite or explode, posing another workplace hazard.
Exposure routes
Food is the main source of aluminium. Drinking water contains more aluminium than solid food;
however, aluminium in food may be absorbed more than aluminium from water.
Major sources of human oral exposure to aluminium include food (due to its use in food additives, food and beverage packaging, and cooking utensils), drinking water (due to its use in municipal water treatment), and aluminium-containing medications (particularly antacid/antiulcer and buffered aspirin formulations). Dietary exposure in Europeans averages to 0.2–1.5 mg/kg/week but can be as high as 2.3 mg/kg/week.
Higher exposure levels of aluminium are mostly limited to miners, aluminium production workers, and Kidney dialysis, dialysis patients.
Consumption of antacids, antiperspirants, vaccines, and cosmetics provide possible routes of exposure.
Consumption of acidic foods or liquids with aluminium enhances aluminium absorption, and maltol has been shown to increase the accumulation of aluminium in nerve and bone tissues.
Treatment
In case of suspected sudden intake of a large amount of aluminium, the only treatment is deferoxamine mesylate which may be given to help eliminate aluminium from the body by chelation.
However, this should be applied with caution as this reduces not only aluminium body levels, but also those of other metals such as copper or iron.
Environmental effects
![Luftaufnahmen Nordseekueste 2012-05-by-RaBoe-478](https://upload.wikimedia.org/wikipedia/commons/c/c2/Luftaufnahmen_Nordseekueste_2012-05-by-RaBoe-478.jpg)
High levels of aluminium occur near mining sites; small amounts of aluminium are released to the environment at the coal-fired power plants or Incineration, incinerators.
Aluminium in the air is washed out by the rain or normally settles down but small particles of aluminium remain in the air for a long time.
Acidic precipitation is the main natural factor to mobilize aluminium from natural sources
and the main reason for the environmental effects of aluminium;
however, the main factor of presence of aluminium in salt and freshwater are the industrial processes that also release aluminium into air.
In water, aluminium acts as a toxiс agent on gill-breathing animals such as fish when the water is acidic, in which aluminium may precipitate on gills, which causes loss of Blood plasma, plasma- and hemolymph ions leading to Osmoregulation, osmoregulatory failure.
Organic complexes of aluminium may be easily absorbed and interfere with metabolism in mammals and birds, even though this rarely happens in practice.
Aluminium is primary among the factors that reduce plant growth on acidic soils. Although it is generally harmless to plant growth in pH-neutral soils, in acid soils the concentration of toxic Al
3+ 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 increases and disturbs root growth and function. Wheat has adaptation, developed a tolerance to aluminium, releasing organic compounds that bind to harmful aluminium cations. Sorghum is believed to have the same tolerance mechanism.
Aluminium production possesses its own challenges to the environment on each step of the production process. The major challenge is the greenhouse gas emissions.
These gases result from electrical consumption of the smelters and the byproducts of processing. The most potent of these gases are Fluorocarbon, perfluorocarbons from the smelting process.
Released sulfur dioxide is one of the primary precursors of acid rain.
Biodegradation of metallic aluminium is extremely rare; most aluminium-corroding organisms do not directly attack or consume the aluminium, but instead produce corrosive wastes. The fungus ''Geotrichum candidum'' can consume the aluminium in compact discs. The bacterium ''Pseudomonas aeruginosa'' and the fungus ''Cladosporium resinae'' are commonly detected in aircraft fuel tanks that use kerosene-based fuels (not avgas), and laboratory cultures can degrade aluminium.
See also
* Aluminium granules
* Aluminium joining
* Aluminium–air battery
* Panel edge staining
* Quantum clock
Notes
References
Bibliography
*
*
*
*
*
*
*
*
*
Further reading
* Mimi Sheller, ''Aluminum Dream: The Making of Light Modernity''. Cambridge, Mass.: Massachusetts Institute of Technology Press, 2014.
External links
Aluminiumat ''The Periodic Table of Videos'' (University of Nottingham)
*
Toxic Substances Portal – Aluminum' – from the Agency for Toxic Substances and Disease Registry, United States Department of Health and Human Services
CDC – NIOSH Pocket Guide to Chemical Hazards – AluminumPrice history of aluminum, according to the IMFHistory of Aluminium– from the website of the International Aluminium Institute
*
{{Authority control
Aluminium,
Chemical elements
Post-transition metals
Rocket fuels, Aluminium
Electrical conductors
Pyrotechnic fuels
Airship technology
Reducing agents
E-number additives
Native element minerals
Chemical elements with face-centered cubic structure