Aluminium

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B

Al

Ga
Appearance
silvery gray metallic


Spectral lines of aluminium
General properties
Name, symbol, number aluminium, Al, 13
Pronunciation UK Listeni/ˌæljʉˈmɪniəm/
AL-ew-MIN-ee-əm;

U.S. Listeni/əˈljmɨnəm/
ə-LEW-mi-nəm

Element category other metal
Group, period, block 133, [[{{{block}}}-block|{{{block}}}]]
Standard atomic weight 26.9815386(13)g·mol−1
Electron configuration [Ne] 3s2 3p1
Electrons per shell 2, 8, 3 (Image)
Physical properties
Phase solid
Density (near r.t.) 2.70 g·cm−3
Liquid density at m.p. 2.375 g·cm−3
Melting point 933.47 K, 660.32 °C, 1220.58 °F
Boiling point 2792 K, 2519 °C, 4566 °F
Heat of fusion 10.71 kJ·mol−1
Heat of vaporization 294.0 kJ·mol−1
Specific heat capacity (25 °C) 24.200 J·mol−1·K−1
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 1482 1632 1817 2054 2364 2790
Atomic properties
Oxidation states 3, 2[1], 1[2]
(amphoteric oxide)
Electronegativity 1.61 (Pauling scale)
Ionization energies
1st: 577.5 kJ·mol−1
2nd: 1816.7 kJ·mol−1
3rd: 2744.8 kJ·mol−1
Atomic radius 143 pm
Covalent radius 121±4 pm
Van der Waals radius 184 pm
Miscellanea
Crystal structure face-centered cubic
Magnetic ordering paramagnetic[3]
Electrical resistivity (20 °C) 28.2 nΩ·m
Thermal conductivity (300 K) 237 W·m−1·K−1
Thermal expansion (25 °C) 23.1 µm·m−1·K−1
Speed of sound (thin rod) (r.t.) (rolled) 5,000 m·s−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
CAS registry number 7429-90-5
Most stable isotopes
Main article: Isotopes of aluminium
iso NA half-life DM DE (MeV) DP
26Al trace 7.17×105 yr β+ 1.17 26Mg
ε - 26Mg
γ 1.8086 -
27Al 100% 27Al is stable with 14 neutrons
A roll of aluminium

Aluminium (or aluminum) is a chemical element. The symbol for aluminium is Al, and its atomic number is 13. Aluminium is the most abundant metal.

Properties[change | edit source]

Aluminium is a very good conductor of electricity and heat. It is light and strong. It can be hammered into sheets (malleable) or pulled out into wires (ductile). It is a highly reactive metal, although it is corrosion resistant.

Aluminium prevents corrosion by forming a small, thin layer of aluminium oxide on its surface. This layer protects the metal by preventing oxygen from reaching it. Corrosion can not occur without oxygen. Because of this thin layer, the reactivity of aluminium is not seen.

Occurrence and preparation[change | edit source]

Bauxite, aluminium ore

Pure aluminium is made from bauxite, a kind of rock that has aluminium oxide and many impurities. The bauxite is crushed and reacted with sodium hydroxide. The aluminium oxide dissolves. Then the aluminum oxide is dissolved in liquid cryolite, a rare mineral. Cryolite is normally produced artificially though. The aluminium oxide is electrolyzed to make aluminium and oxygen.

Aluminium was once considered a precious metal that was even more valuable than gold. This is no longer true because, as technology improved, it became cheaper and easier to make pure metal.

Compounds[change | edit source]

Pure (white) and impure (yellow) forms of aluminium chloride

Aluminium forms chemical compounds in the +3 oxidation state. They are generally unreactive. Aluminium chloride is an example. Very rarely are compounds in the +1 or +2 oxidation state.

Uses[change | edit source]

A computer case made from aluminium

Aluminium has many uses. Much of it is used in overhead power cables. It is also widely used in window frames and aircraft bodies. It is found at home as saucepans, soft drink cans, and cooking foil. Aluminium is also used to coat car headlamps and compact discs.

Pure aluminium is very soft, so a harder metal is almost always added. The harder metal is usually copper. Copper/aluminium alloys are to make ships, because the aluminium prevents corrosion, and the copper prevents barnacles.

Aluminium compounds are used in deodorants, water processing plants, food additives, and antacids.

Recycling[change | edit source]

Aluminium cans ready for recycling at Central European Waste Management's plant in Europe.

Since aluminium needs to be made by electrolysis, it requires a very large amount of electrical power. Recycling aluminium would be much cheaper. That's why recycling plants were opened. The cost of recycling aluminium is much less than the cost of making it from bauxite.

Toxicity[change | edit source]

Aluminium is not used in the human body, although it is very common. People debate whether its use in deodorants and water treatment is healthy. Aluminium ions slow down plant growth in acidic soils. Aluminium may be a factor in Alzheimer's disease (a disease when the brain stops working and the patient is confused).[4][5] But the Alzheimer's Society says overwhelming medical and scientific opinion is that studies have not convincingly demonstrated a causal relationship between aluminium and Alzheimer's disease.[6]

Related pages[change | edit source]

References[change | edit source]

  1. Aluminium monoxide
  2. Aluminium iodide
  3. Lide, D. R. (2000). "Magnetic susceptibility of the elements and inorganic compounds". CRC Handbook of Chemistry and Physics (81st ed.). CRC Press. ISBN 0849304814. http://www-d0.fnal.gov/hardware/cal/lvps_info/engineering/elementmagn.pdf.
  4. Ferreira PC, Piai Kde A, Takayanagui AM, Segura-Muñoz SI (2008). "Aluminum as a risk factor for Alzheimer's disease". Rev Lat Am Enfermagem 16 (1): 151–7. doi:10.1590/S0104-11692008000100023. PMID 18392545. http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-11692008000100023&lng=en&nrm=iso&tlng=en.
  5. Rondeau, V.; Jacqmin-Gadda, H.; Commenges, D.; Helmer, C.; Dartigues, J.-F. (2008). "Aluminum and Silica in Drinking Water and the Risk of Alzheimer's Disease or Cognitive Decline: Findings From 15-Year Follow-up of the PAQUID Cohort". American Journal of Epidemiology 169 (4): 489–96. doi:10.1093/aje/kwn348. PMC 2809081. PMID 19064650.
  6. Aluminium and Alzheimer's disease, The Alzheimer's Society. Retrieved 30 January 2009.

Other websites[change | edit source]