Atomic Number: 31
Atomic Symbol: Ga
Atomic Weight: 69.72
Electron Configuration: -8-18-3
(L. Gallia, France; also from Latin, gallus, a translation of Lecoq, a cock)
Predicted and described by Mendeleev as ekaaluminum, and discovered spectroscopically by Lecoq de Boisbaudran in 1875, who in the same year obtained the free metal by electrolysis of a solution of the hydroxide in KOH.
Gallium is often found as a trace element in diaspore, sphalerite, germanite, bauxite, and coal.
Some flue dusts from burning coal have been shown to contain as much 1.5% gallium.
It is the only metal, except for mercury, cesium, and rubidium, which can be liquid near room temperaturs; this makes possible its use in high-temperature thermometers.
It has one of the longest liquid ranges of any metal and has a low vapor pressure even at high temperatures.
There is a strong tendency for gallium to supercool below its freezing point.
Therefore, seeding may be necessary to initiate solidification.
Ultra-pure gallium has a beautiful, silvery appearance, and the solid metal exhibits a conchoidal fracture similar to glass.
The metal expands 3.1% on solidifying; therefore, it should not be stored in glass or metal containers, as they may break as the metal solidifies.
Gallium wets glass or porcelain and forms a brilliant mirror when it is painted on glass.
It is widely used in doping semiconductors and producing solid-state devices such as transistors.
High-purity gallium is attacked only slowly by mineral acids.
Magnesium gallate containing divalent impurities such as Mn+2 is finding use in commercial ultraviolet activiated powder phosphors.
Gallium arsenide is capable of converting electricity directly into coherent light.
Gallium readily alloys with most metals, and has been used as a component in low-melting alloys.
Its toxicity appears to be of a low order, but should be handled with care until more data are forthcoming.
The metal can be supplied in ultrapure form (99.99999+%). The cost is about $3/g.