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Aluminium - Wikipedia, the Free Encyclopedia Page 1 of 17 Aluminium - Wikipedia, the free encyclopedia Page 1 of 17 Aluminium From Wikipedia, the free encyclopedia (Redirected from Aluminum) Aluminium ( /ˌæljuːˈmɪniəm/ AL-ew-MIN-ee-əm) or aluminum (American English; /ˌəlˈuːmɪnəm/ ə- magnesium ← aluminium → silicon LOO-mi-nəm) is a silvery white member of the boron B 13Al group of chemical elements. It has the symbol Al, and ↑ its atomic number is 13. It is not soluble in water Al under normal circumstances. ↓ Periodic table Ga Aluminium is the third most abundant element (after oxygen and silicon), and the most abundant metal, in Appearance the Earth's crust. It makes up about 8% by weight of silvery gray metallic the Earth's solid surface. Aluminium metal is too reactive chemically to occur natively. Instead, it is found combined in over 270 different minerals.[4] The chief ore of aluminium is bauxite. Aluminium is remarkable for the metal's low density and for its ability to resist corrosion due to the phenomenon of passivation. Structural components made from aluminium and its alloys are vital to the aerospace industry and are important in other areas of transportation and structural materials. The most useful compounds of aluminium, at least on a weight basis, are the oxides and sulfates. Despite its prevalence in the environment, aluminium Spectral lines of aluminium salts are not known to be used by any form of life. In keeping with its pervasiveness, aluminium is well General properties [5] tolerated by plants and animals. Due to their Name, symbol, aluminium, Al, 13 prevalence, potential beneficial (or otherwise) number biological roles of aluminium compounds are of i continuing interest. Pronunciation UK /ˌæljʉˈmɪniəm/ AL-ew-MIN-ee-əm; or US i/əˈluːmɨnəm/ Contents ə-LOO-mi-nəm ■ 1 Characteristics Element category other metal ■ 1.1 Physical Group, period, block 13, 3, p ■ 1.2 Chemical Standard atomic 26.981 5386(13) ■ 1.3 Isotopes ■ 1.4 Natural occurrence weight ■ 2 Production and refinement Electron [Ne] 3s2 3p1 ■ 2.1 Recycling configuration http://en.wikipedia.org/wiki/Aluminum 6/3/2012 Aluminium - Wikipedia, the free encyclopedia Page 2 of 17 ■ 3 Compounds Electrons per shell 2, 8, 3 (Image) ■ 3.1 Oxidation state +3 Physical properties ■ 3.1.1 Halides ■ 3.1.2 Oxide and hydroxides Phase solid ■ 3.1.3 Carbide, nitride, and Density (near r.t.) 2.70 g·cm−3 related materials −3 ■ 3.2 Organoaluminium compounds and Liquid density at m.p. 2.375 g·cm related hydrides Melting point 933.47 K, 660.32 °C, ■ 3.3 Oxidation states +1 and +2 1220.58 °F ■ 3.3.1 Aluminium(I) ■ 3.3.2 Aluminium(II) Boiling point 2792 K, 2519 °C, 4566 °F ■ 3.4 Analysis Heat of fusion 10.71 kJ·mol−1 ■ 4 Applications −1 ■ 4.1 General use Heat of vaporization 294.0 kJ·mol ■ 4.2 Aluminium compounds Molar heat capacity 24.200 J·mol−1·K−1 ■ 4.2.1 Alumina Vapor pressure ■ 4.2.2 Sulfates ■ 4.2.3 Chlorides ■ 4.2.4 Niche compounds P (Pa) 1 10 100 1 k 10 k 100 k ■ 4.3 Aluminium alloys in structural at T (K) 1482 1632 1817 2054 2364 2790 applications ■ 5History ■ 6 Etymology Atomic properties ■ 7 Health concerns Oxidation states 3, 2[1], 1[2] ■ 8 Effect on plants (amphoteric oxide) ■ 9 See also ■ 10 References Electronegativity 1.61 (Pauling scale) ■ 11 External links Ionization energies 1st: 577.5 kJ·mol−1 (more) 2nd: 1816.7 kJ·mol−1 3rd: 2744.8 kJ·mol−1 Characteristics Atomic radius 143 pm Physical Covalent radius 121 ±4 pm Van der Waals radius 184 pm Aluminium is Miscellanea a relatively soft, durable, Crystal structure face-centered cubic lightweight, Magnetic ordering paramagnetic[3] ductile and Electrical resistivity (20 °C) 28.2 nΩ·m malleable −1 −1 metal with Thermal conductivity 237 W·m ·K Etched surface from a high purity appearance −1 −1 (99.9998%) aluminium bar, size Thermal expansion (25 °C) 23.1 µm·m ·K ranging from 55×37 mm Speed of sound (thin (r.t.) (rolled) 5,000 m·s−1 silvery to dull gray, rod) depending on the surface roughness. It is nonmagnetic Young's modulus 70 GPa and does not easily ignite. A fresh film of aluminium Shear modulus 26 GPa http://en.wikipedia.org/wiki/Aluminum 6/3/2012 Aluminium - Wikipedia, the free encyclopedia Page 3 of 17 film serves as a good reflector (approximately 92%) Bulk modulus 76 GPa of visible light and an excellent reflector (as much as Poisson ratio 0.35 98%) of medium and far infrared radiation. The yield strength of pure aluminium is 7–11 MPa, while Mohs hardness 2.75 aluminium alloys have yield strengths ranging from Vickers hardness 167 MPa [6] 200 MPa to 600 MPa. Aluminium has about one- Brinell hardness 245 MPa third the density and stiffness of steel. It is easily machined, cast, drawn and extruded. CAS registry number 7429-90-5 Most stable isotopes Aluminium atoms are arranged in a face-centered cubic (fcc) structure. Aluminium has a stacking-fault Main article: Isotopes of aluminium energy of approximately 200 mJ/m2.[7] iso NA half-life DM DE (MeV) DP Aluminium is a good thermal and electrical 26Al trace 7.17 ×105 a β+ 1.17 26Mg conductor, having 59% the conductivity of copper, both thermal and electrical. Aluminium is capable of ε - 26Mg being a superconductor, with a superconducting γ 1.8086 - critical temperature of 1.2 Kelvin and a critical 27 27 magnetic field of about 100 gauss (10 milliteslas).[8] Al 100% Al is stable with 14 neutrons Chemical Corrosion resistance can be excellent due to a thin surface layer of aluminium oxide that forms when the metal is exposed to air, effectively preventing further oxidation. The strongest aluminium alloys are less corrosion resistant due to galvanic reactions with alloyed copper.[6] This corrosion resistance is also often greatly reduced by aqueous salts, particularly in the presence of dissimilar metals. Owing to its resistance to corrosion, aluminium is one of the few metals that retain silvery reflectance in finely powdered form, making it an important component of silver-colored paints. Aluminium mirror finish has the highest reflectance of any metal in the 200–400 nm (UV) and the 3,000–10,000 nm (far IR) regions; in the 400–700 nm visible range it is slightly outperformed by tin and silver and in the 700– 3000 (near IR) by silver, gold, and copper.[9] Aluminium is oxidized by water to produce hydrogen and heat: 2 Al + 3 H2O → Al2O3 + 3H2 This conversion is of interest for the production. Challenges include circumventing the formed oxide layer which inhibits the reaction and the expenses associated with the storage of energy by regeneration of the Al metal.[10] Isotopes Main article: Isotopes of aluminium http://en.wikipedia.org/wiki/Aluminum 6/3/2012 Aluminium - Wikipedia, the free encyclopedia Page 4 of 17 Aluminium has many known isotopes, whose mass numbers range from 21 to 43; however, only 27Al 26 5 27 (stable isotope) and Al (radioactive isotope, t1/2 = 7.2×10 y) occur naturally. Al has a natural abundance above 99.9%. 26Al is produced from argon in the atmosphere by spallation caused by cosmic- ray protons. Aluminium isotopes have found practical application in dating marine sediments, manganese nodules, glacial ice, quartz in rock exposures, and meteorites. The ratio of 26Al to 10Be has been used to study the role of transport, deposition, sediment storage, burial times, and erosion on 105 to 106 year time scales.[11] Cosmogenic 26Al was first applied in studies of the Moon and meteorites. Meteoroid fragments, after departure from their parent bodies, are exposed to intense cosmic-ray bombardment during their travel through space, causing substantial 26Al production. After falling to Earth, atmospheric shielding drastically reduces 26Al production, and its decay can then be used to determine the meteorite's terrestrial age. Meteorite research has also shown that 26Al was relatively abundant at the time of formation of our planetary system. Most meteorite scientists believe that the energy released by the decay of 26Al was responsible for the melting and differentiation of some asteroids after their formation 4.55 billion years ago.[12] Natural occurrence See also: List of countries by bauxite production Stable aluminium is created when hydrogen fuses with magnesium either in large stars or in supernovae. [13] In the Earth's crust, aluminium is the most abundant (8.3% by weight) metallic element and the third most abundant of all elements (after oxygen and silicon).[14] Because of its strong affinity to oxygen, it is almost never found in the elemental state; instead it is found in oxides or silicates. Feldspars, the most common group of minerals in the Earth's crust, are aluminosilicates. Native aluminium metal can only be found as a minor phase in low oxygen fugacity environments, such as the interiors of certain volcanoes.[15] Native aluminium has been reported in cold seeps in the northeastern continental slope of the South China Sea and Chen et al. (2011)[16] have proposed a theory of its origin as resulting by – [16] reduction from tetrahydroxoaluminate Al(OH)4 to metallic aluminium by bacteria. It also occurs in the minerals beryl, cryolite, garnet, spinel and turquoise. Impurities in Al2O3, such as chromium or iron yield the gemstones ruby and sapphire, respectively. Although aluminium is an extremely common and widespread element, the common aluminium minerals are not economic sources of the metal. Almost all metallic aluminium is produced from the ore bauxite (AlOx(OH)3–2x). Bauxite occurs as a weathering product of low iron and silica bedrock in tropical climatic conditions.[17] Large deposits of bauxite occur in Australia, Brazil, Guinea and Jamaica and the primary mining areas for the ore are in Australia, Brazil, China, India, Guinea, Indonesia, Jamaica, Russia and Suriname.
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