Aluminum

26.98

Aluminum bulkhead of the international space station - NASA

Classification:	Aluminum is a metal
Atomic weight:	26.98154 g/mol
Density @ 20 ^oC:	2.702 g/cm³
Atomic volume:	9.98 cm³/mol

Louis de Morveau believed a new metal could be discovered in the oxide alumina. He was right, but he was unable to isolate it. He did, however, devise the first systematic method of naming chemicals, and, as we can see, he was a pioneering balloonist.

Discovery of Aluminum

Author: Dr. Doug Stewart

Alum (potassium aluminum sulfate) is a white mineral which has been used since ancient times for dyeing and tanning and to stop bleeding.

A particularly stable oxide of aluminum, aluminum oxide - chemical formula (Al₂O₃) - can be obtained from alum. This substance was named alumina by Louis de Morveau in 1760.

De Morveau believed alumina contained a new metallic element, but he was unable to extract this metal, which he called alumine, from its 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 (Woehler) repeated Ørsted's experiment but found it yielded only potassium metal. Wöhler developed the method further 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.

More recently, Fogh repeated the original experiments and has shown that Ørsted's method can give satisfactory results.

This has strengthened the priority of Ørsted's original work and his position as discoverer of aluminum. ⁽⁴⁾

Interesting Facts: Did You Know?

Interesting Facts about Aluminum: Did You Know?

Aluminum is a great metal to recycle. Recyling needs only 5% of the energy used to produce aluminum from its ore, bauxite. ⁽⁵⁾
Aluminum does not stick to magnets under normal conditions.
There is more aluminum in the Earth's crust than any other metal. At about 8 percent, aluminum is the third most abundant element in our planet's crust.
Aluminum is made in the nuclear fires of heavy stars when a proton adds to magnesium. (Magnesium is itself made in stars by nuclear fusion of two carbons.) ⁽⁶⁾

States

State (s, l, g): solid
Melting point: 933.57 K (660.32 ^oC)

Boiling point: 2740 K (2466.85 ^oC)

Energies

Specific heat capacity: 0.90 J g^-1 K^-1
Heat of fusion: 10.790 kJ mol^-1
1^st ionization energy: 577.6 kJ mol^-1
3^rd ionization energy: 2744.7 kJ mol^-1

Heat of atomization: 326 kJ mol^-1
Heat of vaporization: 293.40 kJ mol^-1
2^nd ionization energy: 1816.6 kJ mol^-1
Electron affinity: 42.6 kJ mol^-1

Oxidation & Electrons

Shells: 2,8,3
Minimum oxidation number: 0
Min. common oxidation no.: 0
Electronegativity (Pauling Scale): 1.61

Electron configuration: 1s² 2s² 2p⁶ 3s² 3p¹
Maximum oxidation number: 3
Max. common oxidation no.: 3
Polarizability volume: 8.3 Å³

Appearance & Characteristics

Structure: fcc: face-centered cubic
Hardness: 2.8 mohs

An aluminum block is cut, it's like a hot knife through butter.

Pouring molten aluminum.

Color: silvery
Harmful effects: No proven issues; ingestion may cause alzheimer's disease

Characteristics:
Aluminum is a silvery-white metal. It does not stick to magnets (it is paramagnetic and so its magnetism under normal conditions is very, very weak). It is 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. ⁽⁷⁾

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 & Compounds

Reaction with air: mild, w/ht ⇒ Al₂O₃
Reaction with 15 M HNO₃: passivated
Oxide(s): Al₂O₃
Hydride(s): AlH₃

Reaction with 6 M HCl: mild, ⇒ H₂, AlCl₃
Reaction with 6 M NaOH: mild, ⇒ H₂, [Al(OH)₄]^-
Chloride(s): AlCl₃ & Al₂Cl₆

Radius

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

Ionic radius (1+ ion): pm
Ionic radius (3+ ion): 53.5 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.

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. Paolo Ventura, Roberta Carini, Francesca D'Antona, A deep insight into the Mg-Al nucleosynthesis in massive AGBs and SAGB stars., Mon. Not. R. Astron. Soc., 2002.
6. Burrows et al., Chemistry³, (2009) Oxford University Press, p1201.
7. Dekov et al., American Mineralogist., (2009) 94: p1283-1286.

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