Gallium
Atomic Number: 31
Symbol: Ga
Atomic Weight: 69.732
Discovery: Paul-Emile Lecoq de Boisbaudran 1875 (France)
Electron Configuration: [Ar] 4s2 3d10 4p1
Word Origin: Latin Gallia, France and gallus, a translation of Lecoq, a cock (name of its discoverer was Lecoq de Boisbaudran)
Isotopes: Two isotopes of gallium are known. Gallium-69 accounts for 60.108% of the natural abundance of the element. Gallium-71 accounts for 39.892% of the element's natural abundance.
Properties: Gallium has a melting point of 29.78°C, boiling point of 2403°C, specific gravity of 5.904 (29.6°C), specific gravity of 6.095 (29.8°C, liguid), with a valence of 2 or 3. Gallium has one of the longest liquid temperature ranges of any metal, with a low vapor pressure even at high temperatures. The element has a strong tendency to supercool below its freezing point. Seeding is sometimes necessary to initiate solidification. Pure gallium metal has a silvery appearance. It exhibits a conchoidal fracture that it similar to a glass fracture in appearance. Gallium expands 3.1% on solidifying, so it should not be stored in a metal or glass container that can break upon its solidification. Gallium wets glass and porcelain, forming a brilliant mirror finish on glass. Highly pure gallium is only slowly attacked by mineral acids. Gallium is associated with a relatively low toxicity, but should be handled with care until more health data has been accumulated.
Uses: Since it is a liquid near room temperature, gallium is used for high-temperature thermometers. Gallium is used to dope semiconductors and for producing solid-state devices. Gallium arsenide is used to convert electricity into coherent light. Magnesium gallate with divalent impurities (e.g., Mn2+) is used to make commercial ultraviolet-activated powder phosphors.
Sources: Gallium may be found as a trace element in sphalerite, diaspore, bauxite, coal, and germanite. Flue dusts from burning coal may contain as much as 1.5% gallium. The free metal may be obtained by electrolysis of its hydroxide in a KOH solution.
Element Classification: Metal
Density (g/cc): 5.91
Melting Point (K): 302.93
Boiling Point (K): 2676
Appearance: soft, blue-white metal
Atomic Radius (pm): 141
Atomic Volume (cc/mol): 11.8
Covalent Radius (pm): 126
Ionic Radius: 62 (+3e) 81 (+1e)
Specific Heat (@20°C J/g mol): 0.372
Fusion Heat (kJ/mol): 5.59
Evaporation Heat (kJ/mol): 270.3
Debye Temperature (K): 240.00
Pauling Negativity Number: 1.81
First Ionizing Energy (kJ/mol): 578.7
Oxidation States: 3
Lattice Structure: Orthorhombic
Lattice Constant (Å): 4.510
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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