Aluminum

General:

Name:Aluminum Symbol:Al
Type:Metal Atomic weight:26.98154
Density @ 293 K: 2.702 g/cm3 Atomic volume:9.98 cm3/mol
Discovered:

Alum (potassium aluminum sulfate) is a white mineral used since ancient times for dyeing and tanning and to stop bleeding. Alum yields a particularly stable oxide, (Al2O3). Aluminum oxide was named alumina by Louis de Morveau in 1760. De Morveau was unable to extract the metal, which he called alumine, from the oxide. (1), (2)

In 1807 or 1808, Humphry Davy decomposed alumina (Al2O3) in an electric arc to obtain a metal. The metal was not pure aluminum, but an alloy of aluminum and iron. Davy called the new metal alumium, then renamed it aluminum. (3)

Aluminum was first isolated in 1825 by Hans Christian Ørsted (Oersted) who reported, "a lump of metal which in color and luster somewhat resembles tin". Ørsted produced aluminum by reducing aluminum chloride using a potassium-mercury amalgam. The mercury was removed by heating to leave aluminum. Friedrich Wöhler (Wohler) repeated Ørsted's experiment but found it yielded only potassium metal. Wöhler developed the further method two years later, reacting volatalized aluminum trichloride with potassium to produce small amounts of aluminum.(1)

In 1856 Berzelius stated that it was Wöhler who had succeeded in 1827. Wöhler is therefore usually given credit for the discovery, but Fogh has put forward a strong claim of priority on behalf of Ørsted, and has shown that Ørsted's method can give satisfactory results. (4)

States

State (s, l, g):solid
Melting point:933.57 K (660.32 °C) Boiling point: 2740 K (2466.85 °C)

Energies

Specific heat capacity:0.90 J g-1 K-1 Heat of atomization:326 kJ mol-1
Heat of fusion:10.790 kJ mol-1 Heat of vaporization :293.40 kJ mol-1
1st ionization energy:577.6 kJ mol-1 2nd ionization energy:1816.6 kJ mol-1
3rd ionization energy:2744.7 kJ mol-1 Electron affinity:42.6 kJ mol-1

Oxidation & Electrons

Shells:2,8,3 Electron configuration: [Ne] 3s2 3p1
Minimum oxidation number:0 Maximum oxidation number:3
Min. common oxidation no.:0 Max. common oxidation no.:3
Electronegativity (Pauling Scale):1.61 Polarizability volume: 8.3 Å3

Appearance & Characteristics

Structure: fcc: face-centered cubic Color:silvery
Hardness: 2.8 mohs
Harmful effects:

No proven issues; ingestion may cause alzheimer's disease.

Characteristics:

Aluminum is a silvery-white metal. It is non-magnetic and an excellent electrical conductor. It is of low density and high ductility. It is too reactive to be commonly found as the metal although, very rarely, the native metal can be found. (5)

Aluminum's appearance is dulled and its reactivity is passivated by a film of aluminum oxide that naturally forms on the surface of the metal under normal conditions. The oxide film results in a material that resists corrosion. The film can be thickened using electrolysis or oxidizing agents and aluminum in this form will resist attack by dilute acids, dilute alkalis and concentrated nitric acid.

Aluminum lies sufficiently far on the right side of the periodic table that it shows some hints of nonmetal behavior, reacting with hot alkalis to form aluminate ions [Al(OH)4]- as well as the more typical metal reaction with acids to release hydrogen gas and form the positively charged metal ion, Al3+. i.e. aluminum is amphoteric.

Pure aluminum is quite soft and lacking in strength. Aluminum used in commercial applications has small amounts of silicon and iron (less than 1%) added, resulting in greatly improved strength and hardness.


Uses:

As a result of its low density, low cost, and corrosion resistance, aluminum is widely used around the world.

It is used in an extensive range of products from drinks cans to window frames and boats to aircraft. A Boeing 747-400 contains 147,000 pounds (66,150 kg) of high-strength aluminum.

Unlike some metals, aluminum has no aroma - hence its widespread use in food packaging and cooking pots.

Although not quite as good as silver or copper, aluminum is an excellent electrical conductor. It is also considerably cheaper and lighter than these metals, so it is used widely in overhead power lines.

Of all the metals, only iron is used more widely than aluminum.

Reactions

Reaction with air:mild, w/ht ? Al2O3 Reaction with 6 M HCl:mild, ? H2, AlCl3
Reaction with 15 M HNO3: passivated Reaction with 6 M NaOH:mild, ⇒ H2, [Al(OH)4]-

Compounds

Oxide(s):Al2O3 Chloride(s):AlCl3 & Al2Cl6
Hydride(s):AlH3

Radius

Atomic radius:125 pm Ionic radius (1+ ion): pm
Ionic radius (2+ ion): pm Ionic radius (3+ ion):53.5 pm
Ionic radius (2- ion): pm Ionic radius (1- ion): pm

Conductivity

Thermal conductivity:237 W m-1 K-1 Electrical conductivity:37.6676 x 106 S m-1

Abundance & Isotopes

Abundance earth's crust:8.23 % by weight, 6.32 % by moles
Abundance solar system:56 ppm by weight, 2.7 ppm by moles
Cost, pure:$15.72 per 100g
Cost, bulk:$0.20 per 100g
Source:

Aluminum is the most abundant metal in the earth's crust and the third most element in the earth's crust, after oxygen and silicon. Aluminum is too reactive to be found pure. Bauxite (mainly aluminum oxide) is the most important ore.

Isotopes:

15 whose half-lives are known, mass numbers 22 to 35. Of these, only two occur naturally: 27Al, which is stable, and 26Al, which is radioactive with half-life is 7.17 x 105 years. 26Al is formed by cosmic-ray bombardment of argon in earth's atmosphere.

Other

Other:

References
1. Ian McNeil, Encyclopaedia of the History of Technology., (1996) p102. Routledge
2. David R. Lide, CRC Handbook of Chemistry and Physics., (2007) 4-3. CRC
3. Halvor Kvande, Two hundred years of aluminum ... or is it aluminium?, Journal of the Minerals, Metals and Materials Society, (2008) Volume 60, Number 8: p23-24.
4. http://www.nature.com/nature/journal/v135/n3417/abs/135638b0.html
5. Dekov et al., American Mineralogist., (2009) 94: p1283-1286.

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