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About Aluminum

Aluminum Bohr

Compounds called alums--latin for “bitter salt”-- were used in dyes and wound dressing in ancient Greece and Rome. When the existence of a base metal of these salts was recognized in 1808 by Humphry Davy, he named it alumium, which was eventually changed to aluminum. The metal was first purified by another chemist in 1825, but it was initially very difficult to extract the metal from ore, and for some years this made pure aluminum very valuable. In the late 1880’s, two independent chemists developed what came to be known as the Hall-Heroult process for extracting aluminum from minerals, making extraction much more economical and bringing the metal into more general use.

Aluminum is the third most abundant element in the earth’s crust and the most abundant metal. As such, the element and its compounds have practically innumerable applications. The elemental metal is durable, lightweight, ductile, and malleable, and therefore can be easily formed using a variety of metalworking techniques. However, pure aluminum is soft and lacking in strength, and therefore alloys of aluminum with other metals are generally used for most applications--even household aluminum foil and aluminum beverage cans are generally produced from alloys. Aluminum alloys are generally less dense than alternative metals of similar strength, and thus are particularly useful in applications where a strong but lightweight structure is needed. These alloys are used in the construction of vehicles and buildings, and are frequently the casing material for small electronics. Additionally, aluminum is a component of the magnetic alloys MKM steel and Alnico, which are both used to produce permanent magnets for a variety of uses. Aluminum is also a good thermal and electrical conductor, leading it to find uses as heatsinks and wiring in electronics.

Aluminum oxide, often called alumina, is one of the most common aluminum compounds. Its crystalline form occurs naturally as corundum, high-quality forms of which are used as gemstones and considered either rubies or sapphires depending on the colors imparted by trace impurities. These gems are the hardest natural substances after diamond, and are therefore extremely resistant to scratching. Synthetic versions are used in optical devices such as spectroscopes and lasers, shatter resistant windows, and as insulating substrates for silicon integrated circuits. Powdered forms of aluminum oxide are used as filler in plastics, as it is both white and fairly chemically inert. The same properties lead to its use in sunscreens and cosmetic products. The powder is also used as an abrasive in industrial and commercial applications from sandpaper to toothpaste, and as a catalyst or catalyst support for some industrial chemical processes. Alumina may be used in the production of zirconia aluminia, an extremely strong and corrosion resistant class of composite ceramics that are used in medical implants and cutting tools. Finally, alumina fibers are components of many experimental and a few commercial fiber composite materials, and alumina nanofibers specifically have attracted a great deal of research interest.

Aluminum silicates are also aluminum compounds of considerable commercial importance. A number of aluminosilicates occur naturally, often as microporous minerals known as zeolites or hydrated clay minerals such as kaolin. Natural zeolites can be used industrially, but most applications use synthetic zeolites. Zeolites are notable for their very regular pore sizes, which allow them to act as molecular sieves, separating mixtures based on particle size.This property is exploited for applications in water purification, research chemistry, and the precise separation of gases from mixed gas streams. Additionally, the mineral’s porous nature allows it to filter select ions from nuclear waste, which can then be trapped permanently by pressing the mineral into a non-porous durable ceramic. Zeolites can also efficiently store heat, and are therefore used in heating, refrigeration, and energy storage applications. The high surface area provided by the porous material makes zeolites an excellent catalyst support material. Additionally, zeolites are used in laundry detergent, concrete and cement, medical applications, agriculture, and in aquarium filters and cat litter. Aluminosilicates are also frequently used to produce ceramics; notably, kaolin clay is the base material for the well-known ceramic porcelain.

There are many other notable aluminum compounds. Aluminum sulfates and alums are used in water treatment, paper manufacturing, fabric dying, fireproofing, and leather tanning. Aluminum chloride is used as a catalyst in oil refining and the production of synthetic rubber and polymers, while aluminum chlorohydrate is used in antiperspirants and in water treatment applications. Aluminum is a component of the semiconductor aluminum gallium arsenide, which is often used alongside gallium arsenide in semiconductor devices, and of antimony-aluminum phase change material used in phase-change memory devices. Lanthanum aluminate is a pervoskite ceramic that is of interest for use as a substrate for the growth of superconducting thin-films, and as a gate dielectric for use in next-generation metal oxide semiconductor field-effect transistors (MOSFETs).

Aluminum has a strong affinity for oxygen and is therefore rarely found in its pure state in nature. It is instead found primarily as oxides and silicates, and the primary commercial ore of aluminum is a mix of minerals known as bauxite. The Hall-Heroult process developed in the 19th century is still used today for the processing of aluminum ore. The process requires a significant amount of energy input, but all proposed alternatives have either been less viable economically or were ruled out due to environmental concerns. Since aluminum can be recycled for a fraction of the energy cost of removing new aluminum from ore, aluminum recycling is economically efficient and practiced widely. The “secondary” aluminum produced from recycling therefore accounts for a sizable percentage of the aluminum used each year. Additionally, a number of aluminum-containing minerals are mined for direct use or use as compounds, rather than for extraction of metallic aluminum.

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Semiconductor & Optical
Sputtering Targets

Aluminum is available as metal and compounds with purities from 99% to 99.9999% (ACS grade to ultra-high purity) in the form of foils, sputtering targets, and nanopowders. Elemental or metallic forms include pellets, rod, wire and granules for evaporation source material purposes.High Purity (99.999%) Aluminum Oxide (Al2O3) Powder Aluminum oxide is available in forms including powders and dense pellets for such uses as optical coating and thin film applications. High Purity (99.9999%) Aluminum (Al) Sputtering Target Aluminum is available in soluble forms including chlorides, nitrates and acetates. These compounds are also manufactured as solutions at specified stoichiometries. Aluminum may be synthesized in ultra-high purity (99.999+%) forms for laboratory standards, advanced electronic, thin film deposition using sputtering targets and evaporation materials, metallurgy and optical materials and other high technology applications. Organometallic aluminum compounds are soluble in organic or non-aqueous solvents. Information is provided for stable (non-radioactive) aluminum isotopes in the isotopes tab above. See Analytical Services for information on available certified chemical and physical analysis techniques including MS-ICP, X-Ray Diffraction, PSD and Surface Area (BET) analysis.

Aluminum Properties

Elemental AluminumAluminum (Al) atomic and molecular weight, atomic number and elemental symbolAluminum, also known as Aluminium, is a Block P, Group 13, Period 3 element. It is the third most abundant element in the earth's crust and the most abundant metallic element. In its elemental form, CAS 7429-90-5, Aluminum has a silvery gray metallic appearance. Pure aluminum is soft and lacks strength, but alloyed with small amounts of copper, magnesium, silicon, manganese, or other elements it has extraordinarily useful properties. Aluminum Bohr ModelIt is light, nonmagnetic and non-sparking. It is second among metals in the scale of malleability, and sixth in ductility. Metallic aluminum was first predicted to be a component of alum salts in 1808 by Humphry Davy, and was first isolated in pure form by Friedrich Wöhler in 1827.

Symbol: Al
Atomic Number: 13
Atomic Weight: 26.98
Element Category: post-transition metal
Group, Period, Block: 13, 3, p
Color: silvery
Other Names: Aluminium; Alluminio
Melting Point: 660.32 °C, 1220.58 °F
Boiling Point: 2519 °C, 4566 °F
Density: 2.70 g/cm3
Liquid Density @ Melting Point: 2.375 g/cm3
Density @ 20°C: 2.702 g/cm3
Density of Solid: 2700 kg·m3
Specific Heat: 0.91 (kJ/kg K)
Superconductivity Temperature: 1.175 [or -271.975 °C (-457.55 °F)] K
Triple Point: N/A
Critical Point: 7,577 °C (7,850 K) , Mpa
Heat of Fusion (kJ·mol-1): 10.67
Heat of Vaporization (kJ·mol-1): 290.8
Heat of Atomization (kJ·mol-1): 324.01
Thermal Conductivity: 237 W·m-1·K-1
Thermal Expansion: (25 °C) 23.1 µm·m-1·K-1
Electrical Resistivity: (20 °C) 28.2 nΩ·m
Tensile Strength: 6800 psi Coldroled 16,000 psi.
Molar Heat Capacity: 24.200 J·mol-1·K-1
Young's Modulus: 70 GPa
Shear Modulus: 26 GPa
Bulk Modulus: 76 GPa
Poisson Ratio: 0.35
Mohs Hardness: 2.75
Vickers Hardness: 167 MPa
Brinell Hardness: 245 MPa
Speed of Sound: r.t. (rolled) 5,000 m·s-1
Pauling Electronegativity: 1.61
Sanderson Electronegativity: 1.71
Allred Rochow Electronegativity: 1.47
Mulliken-Jaffe Electronegativity: 1.83 (sp2 orbital)
Allen Electronegativity: 1.613
Pauling Electropositivity: 2.39
Reflectivity (%): 71
Refractive Index: N/A
Electrons: 13
Protons: 13
Neutrons: 14
Electron Configuration: [Ne] 3s2 3p1
Atomic Radius: 143 pm
Atomic Radius,
non-bonded (Å):
Covalent Radius: 121 ± 4 pm
Covalent Radius (Å): 1.24
Van der Waals Radius: 184 pm
Oxidation States: 3,2,1 (amphoteric oxide)
Phase: Solid
Crystal Structure: face-centered cubic
Magnetic Ordering: paramagnetic
Electron Affinity (kJ·mol-1) 41.747
1st Ionization Energy: 577.54 kJ·mol-1
2nd Ionization Energy: 1816.69 kJ·mol-1
3rd Ionization Energy: 2744.80 kJ·mol-1
CAS Number: 7429-90-5
EC Number: 231-072-3
MDL Number: MFCD00134029
Beilstein Number: N/A
SMILES Identifier: [Al]
InChI Identifier: InChI=1S/Al
PubChem CID: 5359268
ChemSpider ID: 4514248
Earth - Total: 1.41%
Mercury - Total: 1.08%
Venus - Total: 1.48%
Earth - Seawater (Oceans), ppb by weight: 5
Earth - Seawater (Oceans), ppb by atoms: 1.1
Earth -  Crust (Crustal Rocks), ppb by weight: 82000000
Earth -  Crust (Crustal Rocks), ppb by atoms: 63000000
Sun - Total, ppb by weight: 60000
Sun - Total, ppb by atoms: 3000
Stream, ppb by weight: 400
Stream, ppb by atoms: 15
Meterorite (Carbonaceous), ppb by weight: 9300000
Meterorite (Carbonaceous), ppb by atoms: 6700000
Typical Human Body, ppb by weight: 900
Typical Human Body, ppb by atom: 210
Universe, ppb by weight: 50000
Universe, ppb by atom: 2000
Discovered By: Sir Humphrey Davy
Discovery Date: 1812
First Isolation: Friedrich Wöhler (1827)

Health, Safety & Transportation Information for Aluminum

Safety data for aluminum metal, nanoparticles, and compounds can vary widely depending on the form. For potential hazard information, toxicity, and road, sea and air transportation limitations, such as DOT Hazard Class, DOT Number, EU Number, NFPA Health rating and RTECS Class, please see the specific aluminum material or compound referenced in the “Products” tab. The below information applies to elemental (metallic) Auminum.

Safety Data
Material Safety Data Sheet MSDS
Signal Word Warning
Hazard Statements H228
Hazard Codes F
Risk Codes 11
Safety Precautions N/A
RTECS Number BD0330000
Transport Information UN 1396 4.3/PG 2
WGK Germany nwg
Globally Harmonized System of
Classification and Labelling (GHS)

Aluminum Isotopes

Aluminum has 22 known isotopes from 21Al to 42Al. Of the 22, only 27Al (stable isotope) and 26Al (radioactive isotope; t1/2 = 0.72x106 yr) occur naturally. 26Al is produced from argon in the atmosphere by spallation caused by cosmic-ray protons. 26Al and 27Al have several practical applications; for example, dating of marine sediments, glacial ice, and meteorites. The ratio of 26Al to 10Be has been used to study the role of transport, deposition, sediment storage and burial times, and erosion on 105 to 106 yr timescales.

Nuclide Isotopic Mass Half-Life Mode of Decay Nuclear Spin Magnetic Moment Binding Energy (MeV) Natural Abundance
(% by atom)
21Al 21.02804(32)# <35 ns p to 20Mg 1/2+# N/A 128.98 -
22Al 22.01952(10)# 59(3) ms ß+ to 22Mg; ß+ + 2p to 20Ne; ß+ + p to 21Na (3)+ N/A 145.44 -
23Al 23.007267(20) 470(30) ms ß+ to 23Mg; ß+ + p to 22Na 5/2+# N/A 164.7 -
24Al 23.9999389(30) 2.053(4) s EC + a to 20Ne; EC to 24Mg 4+ 3.646 180.23 -
25Al 24.9904281(5) 7.183(12) s EC to 25Mg 5/2+ N/A 196.7 -
26Al 25.98689169(6) 7.17(24)E+5 y EC to 26Mg 5+ N/A 208.5 -
27Al 26.98153863(12) STABLE - 5/2+ 3.641504 221.24 100
28Al 27.98191031(14) 2.2414(12) min ß- to 28Si 3+ 3.24 229.32 -
29Al 28.9804450(13) 6.56(6) min ß- to 29Si 5/2+ N/A 238.33 -
30Al 29.982960(15) 3.60(6) s ß- to 30Si 3+ N/A 244.54 -
31Al 30.983947(22) 644(25) ms ß- to 31Si; ß- + n to 30Si (3/2,5/2)+ N/A 251.69 -
32Al 31.98812(9) 31.7(8) ms ß- to 32Si; ß- + n to 31Si 1+ N/A 255.11 -
33Al 32.99084(8) 41.7(2) ms ß- to 33Si; ß- + n to 32Si (5/2+)# N/A 261.33 -
34Al 33.99685(12) 56.3(5) ms ß- to 34Si; ß- + n to 33Si 4-# N/A 263.82 -
35Al 34.99986(19) 38.6(4) ms ß- to 35Si; ß- + n to 34Si 5/2+# N/A 269.1 -
36Al 36.00621(23) 90(40) ms ß- to 36Si; ß- + n to 35Si N/A N/A 270.66 -
37Al 37.01068(36) 10.7(13) ms ß- to 37Si 3/2+ N/A 275.01 -
38Al 38.01723(78) 7.6(6) ms ß- to 38Si N/A N/A 276.57 -
39Al 39.02297(158) 7.6(16) ms ß- to 39Si 3/2+# N/A 279.99 -
40Al 40.03145(75)# 10# ms [>260 ns] Unknown N/A N/A 279.68 -
41Al 41.03833(86)# 2# ms [>260 ns] Unknown 3/2+# N/A 281.24 -
42Al 42.04689(97)# 1# ms Unknown N/A N/A 281.86 -