Gallium

Gallium is a chemical element with the symbol Ga and atomic number 31. It is a soft, silvery-blue post-transition metal in group 13 of the periodic table. Gallium was independently discovered in 1875 by the French chemist Paul-Émile Lecoq de Boisbaudran, who extracted it from zinc ore. The name derives from Gaul, the Latin name for France.

A distinctive feature of gallium is its very low melting point: 29.76 °C. It can melt in the hand, and it remains liquid over a wide range of temperatures before boiling at about 2,204 °C. Gallium expands slightly when it freezes, unlike most metals. In air it quickly forms a thin, protective oxide layer that slows further corrosion. In its solid form it has a density of about 5.91 g/cm³, while liquid gallium is significantly less dense, about 3.53 g/cm³.

Occurrence and production of gallium are unusual because the element is not found free in nature. It occurs only in trace amounts in minerals such as bauxite and sphalerite, and it is primarily recovered as a byproduct of refining aluminum and zinc. Major producing countries include China, Germany, Kazakhstan, and Russia.

Uses of gallium are dominated by electronics and optoelectronics. It is a key constituent of gallium arsenide (GaAs) and gallium nitride (GaN), which are essential for high-speed electronics, lasers, and light-emitting diodes. Gallium alloys, including the room-temperature GaInSn eutectic, are used in low-melting applications and as liquid metal coolants in demonstrations and specialized equipment.

Naturally occurring gallium has two stable isotopes, 69Ga and 71Ga. Metallic gallium is considered of relatively low toxicity, but compounds should be handled with standard laboratory care.