Ga - Atomic Number 31
Gallium is normally a by-product of the manufacture of aluminum. The purification of bauxite by the Bayer process produces an alkaline solution, which can through a series of electrolytic processes result in liquid gallium metal. It can also be recovered during the smelting process of some zinc ores.
APPLICATIONS OF GALLIUM
Electronic and Electromotive:  Gallium nitride (GaN) and gallium arsenide (GaAs) are semiconductors and appear in compounds used in light-emitting diodes (LEDs). Gallium nitride (GaN) emits blue light in LEDs and is a key component in blue laser devices that have become very popular. Other applications include transistors, the manufacture of ultra-high speed logic chips, and for low-noise microwave preamplifiers. It has been suggested that a liquid gallium-tin alloy could be used to cool computer chips in place of water. The GaAs and GaN used in electronic components, representing about 98% of the gallium consumption in the US.
Energy: Gallium is one of the new photovoltaic compounds - copper indium gallium selenium sulfide or CIGS, used to produce thin film solar panels, as an efficient alternative to crystalline silicon.
Aluminum-gallium alloy can potentially provide a solid hydrogen source for transportation purposes, effectively a hydrogen fuel cell.  Aluminum tends to react with water to produce hydrogen, while it forms aluminum oxide - an unwanted protective coat which prevents further reaction. When gallium is alloyed with aluminum, this coating does not form.
Science and Medicine: Gallium issued in metal-in-glass high-temperature thermometers. A low temperature liquid eutectic alloy of gallium, indium, and tin, is widely available in medical thermometers (fever thermometers), replacing problematic mercury.
Gallium citrate and gallium nitrate are used as radiopharamaceutical agents in a nuclear medicine imaging procedure commonly referred to as a gallium scan.
Gallium-68 has been used as an experimental positron emitting gallium isotope, in a PET scan technique which combines features of the gallium scan and the CT/PET scan.
Gallium nitrate is also used as an intravenous pharmaceutical to treat hypercalcemia associated with tumor metastasis to bones and gallium maltolate is used in clinical and preclinical trials as a potential treatment for cancer, infectious disease, and inflammatory diseases.  Research is being conducted to determine whether gallium can be used to fight bacterial infections in people with cystic fibrosis.
Some research is being devoted to gallium alloys as substitutes for mercury dental amalgam, but these compounds have yet to see wide acceptance.
Industrial Products: Gallium is used to create brilliant mirrors as gallium wets glass or porcelain.  It readily alloys with most metals, and has been used as a component in low-melting temperature alloys and added in quantities up to 2% in common solders can aid their wetting and flow characteristics.