Gallium

Lore & Background

Gallium does not occur as a free element in nature, but rather as gallium(III) compounds in trace amounts in zinc ores such as sphalerite and in bauxite. It is easily obtained by smelting. Very pure gallium is a silvery blue metal that fractures conchoidally like glass. Its stable phase (Ga-I) is a complex orthorhombic structure with eight atoms in the conventional unit cell, and the bonding between the two nearest neighbors is covalent, forming Ga2 dimers. This explains its low melting point relative to neighbor elements aluminium and indium.

Reader's Guide

Gallium is predominantly used in electronics. Gallium arsenide, the primary chemical compound of gallium in electronics, is used in microwave circuits, high-speed switching circuits, and infrared circuits. Semiconducting gallium nitride and indium gallium nitride produce blue and violet light-emitting diodes and diode lasers. Gallium is also used in the production of artificial gadolinium gallium garnet for jewelry. Gallium alloys with low temperatures are used in thermometers as a non-toxic and environmentally friendly alternative to mercury. It has no known natural role in biology, but gallium(III) behaves similarly to ferric salts in biological systems and has been used in some medical applications, including pharmaceuticals and radiopharmaceuticals.

Did You Know?

• Gallium is one of only four non-radioactive metals that are liquid at or near normal room temperature, along with caesium, rubidium, and mercury.
• Gallium's volume expands by 3.10% when it changes from a liquid to a solid, so care must be taken when storing it.
• Gallium has 30 known isotopes, but only two are stable and occur naturally: gallium-69 and gallium-71.
• Liquid gallium wets glass and skin, making it mechanically difficult to handle, but it is substantially less toxic than mercury.