Aluminium (aluminum in North American English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals; about one-third that of steel. It has a great affinity towards oxygen, forming a protective layer of oxide 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, nonmagnetic and ductile. It has one stable isotope: 27Al, which is highly abundant, making aluminium the twelfth-most common element in the universe. The radioactivity of 26Al is used in radiometric dating.

Chemically, aluminium is a post-transition metal in the boron group; as is common for the group, aluminium forms compounds primarily in the +3 oxidation state. The aluminium cation Al3+ is small and highly charged; as such, it has more polarizing power, and bonds formed by aluminium have a more covalent character. The strong affinity of aluminium for oxygen leads to the common occurrence of its oxides in nature. Aluminium is found on Earth primarily in rocks in the crust, where it is the third-most abundant element, after oxygen and silicon, rather than in the mantle, and virtually never as the free metal. It is obtained industrially by mining bauxite, a sedimentary rock rich in aluminium minerals.

The discovery of aluminium was announced in 1825 by Danish physicist Hans Christian Ørsted. The first industrial production of aluminium was initiated by French chemist Henri Étienne Sainte-Claire Deville in 1856. Aluminium became much more available to the public with the Hall–Héroult process developed independently by French engineer Paul Héroult and American engineer Charles Martin Hall 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 for aviation. In 1954, aluminium became the most produced non-ferrous metal, surpassing copper. 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 for metabolism, 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.

© Wikipedia | CC-by-SA-3.0 | Read more …

Atomic properties

Standard atomic weight26.9815 ±3·10-7
Atomic mass26.9815 u

Atomic radii

Radius (empirical)143 pm
Radius (calculated)118 pm
Covalent radius121 ±4 pm
Van der Waals radius184 pm

Atomic shell

Electron configurationNe 3s2 3p1
Ionization energy(1st) 5.985769 eV
(2nd) 18.82855 eV
(3rd) 28.447642 eV
(4th) 119.9924 eV
(5th) 153.8252 eV
Shell model

Physical properties

Density2.698 g·cm−3 (293.1 K)
Molar volume1·10-5 m3·mol−1
Speed of sound5,100 m·s−1


Melting point933.4 K
Boiling point2,743 K
Liquid range1,809 K
Transition temperature1.18 K


Melting enthalpy10.7 kJ·mol-1
Enthalpy of vaporization293 kJ·mol-1
Binding energy326 kJ·mol-1

Heat and conductivity

Specific heat capacity897 J·kg−1·K−1
Thermal conductivity235 W·m-1·K-1
Expansion coefficient2.31·10-5 K-1
Work function4.16 [4.06 … 4.26] eV


Mohs hardness2.75
Brinell hardness245 NM·m-2
Vickers hardness167 NM·m-2

Elastic properties

Young’s modulus70 GPa
Shear modulus26 GPa
Bulk modulus76 GPa
Poisson’s ratio0.35

Electrical properties

Electrical conductivity3.77·107 S·m-1
Resistance2.7·10-8 Ωm


Magnetic susceptibility1.65·10-5 cm3·mol−1

Optical properties

Reflectivity71 %

Chemical properties

Oxidation state1, 2, 3
Standard potential-1.676 V (Al3+ + 3e- → Al)


Pauling scale1.61
Sanderson scale1.71
Allred-Rochow scale1.47
Mulliken scale1.83
Allen scale1.613
Ghosh-Gupta scale4.639 eV
Boyd-Edgecombe scale1.58
Nagle scale1.55
Pearson absolute negativity3.23 eV

Other properties

Natural occurrenceprimordial
Crystal structureFace-centered cubic
Goldschmidt Classificationlithophile
Superconductorwith transition tempperature (solid body, normal pressure)
Price/kg1.79 USD

Natural abundances

50,000 ppb ≈ 5.02·1014 M☉
60,000 ppb ≈ 1.19·1014 Mt
9.3·106 ppb ≈ 9.29 kg
Earth’s crust
8.2·107 ppb ≈ 2.27·109 Mt
5 ppb ≈ 6.85 Gt
Flowing water
400 ppb ≈ 6.4 Gt
Human body
900 ppb ≈ 63 mg