Arsenic
Atomic Number: 33
Symbol: As
Atomic Weight: 74.92159
Discovery: Albertus Magnus 1250? Schroeder published two methods of preparing elemental arsenic in 1649.
Electron Configuration: [Ar] 4s2 3d10 4p3
Word Origin: Latin arsenicum and Greek arsenikon: yellow orpiment, identified with arenikos, male, from the belief that metals were different sexes; Arabic Az-zernikh: the orpiment from Persian zerni-zar, gold
Properties: Arsenic has a valence of -3, 0, +3, or +5. The elemental solid primarily occurs in two modifications, though other allotropes are reported. Yellow arsenic has a specific gravity of 1.97, while gray or metallic arsenic has a specific gravity of 5.73. Gray arsenic is the usual stable form, with a melting point of 817°C (28 atm) and sublimation point at 613°C. Gray arsenic is a very brittle semi-metallic solid. It is steel-gray in color, crystalline, tarnishes readily in air, and is rapidly oxidized to arsenous oxide (As2O3) upon heating (arsenous oxide exudes the odor of garlic). Arsenic and its compounds are poisonous.
Uses: Arsenic is used as a doping agent in solid-state devices. Gallium arsenide is used in lasers which convert electricity into coherent light. Arsenic is used pyrotechny, hardening and improving the sphericity of shot, and in bronzing. Arsenic compounds are used as insecticides and in other poisons.
Sources: Arsenic is found in its native state, in realgar and orpiment as its sulfides, as arsenides and sulfaresenides of heavy metals, as arsenates, and as its oxide. The most common mineral is Mispickel or arsenopyrite (FeSAs), which can be heated to sublime arsenic, leaving ferrous sulfide.
Element Classification: Semimetallic
Density (g/cc): 5.73 (grey arsenic)
Melting Point (K): 1090
Boiling Point (K): 876
Appearance: steel-gray, brittle semimetal
Atomic Radius (pm): 139
Atomic Volume (cc/mol): 13.1
Covalent Radius (pm): 120
Ionic Radius: 46 (+5e) 222 (-3e)
Specific Heat (@20°C J/g mol): 0.328
Evaporation Heat (kJ/mol): 32.4
Debye Temperature (K): 285.00
Pauling Negativity Number: 2.18
First Ionizing Energy (kJ/mol): 946.2
Oxidation States: 5, 3, -2
Lattice Structure: Rhombohedral
Lattice Constant (Å): 4.130
References: Los Alamos National Laboratory (2001), Crescent Chemical Company (2001), Lange's Handbook of Chemistry (1952), CRC Handbook of Chemistry & Physics (18th Ed.)
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