Gallium

Ga
Atomic No. - 31

Gallium metal expands by 3.1% when it solidifies, and therefore should not be stored in either glass or metal containers.

The History Says

Gallium was discovered spectroscopically by Lecoq de Boisbaudran in the year 1875 by its characteristic spectrum, i.e. two violet lines, in an examination of a zinc blend from the Pyrenees.

The Present Scenario

Gallium is used in some high temperature thermometers, and a eutectic alloy of gallium, indium, and tin is widely available in fever thermometers, replacing mercury.

---

Gallium is a rare, soft silvery metallic poor metal which is a brittle solid at low temperatures and turns to liquid state slightly above room temperature, thus melting in hand. Gallium occurs in a trace amount in bauxite and zinc ores.

Like water, it expands while freezing, becoming less dense. Though gallium is non-toxic, but studies have showed that it is even not useful to living organisms. It can corrode most metals by diffusing into their metal lattice. Gallium do not crystallizes in any of the simple crystal structures. Under normal conditions, the stable phase is orthorhombic with 8 atoms in the conventional unit cell.

The name 'gallium' is supposed to be derived from the Latin word for France, Gallia. Another theor suggests that Paul-Emile Lecoq de Boisbaudran, the discoverer of Gallium has taken the name from the Latin word 'gallum,' which mean 'the cock,' can be from his own name, Lecoq.

Physical Properties of Gallium

Phase	Solid
Density (near room temperature)	5.91 g/cm3
Liquid density at melting point	6.095 g/cm3
Melting point	302.9146 K (29.7646°C, 85.5763°F)
Boiling point	2477 K (2204°C, 3999°F)
Heat of fusion	5.59 kJ/mol
Heat of vaporization	254 kJ/mol
Heat of capacity	(25°C) 25.86 J/(mol-K)

Atomic Properties of Gallium

Crystal structure	Orthorhombic
Oxidation states	3 (amphoteric oxide)
Electronegativity	1.81 (Pauling scale)
Ionization energies	1st: 578.8 kJ/mol 2nd: 1979.3 kJ/mol 3rd: 2963 kJ/mol
Atomic radius	130 pm
Atomic radius (calc.)	136 pm
Covalent radius	126 pm
Van der Waals radius	187 pm

Uses of Gallium

• In integrated circuits with optoelectronic devices.
• In creating brilliant mirrors.
• To dope semiconductors and produce solid-state devices such as transistors.
• As a component in low-melting alloys.
• In some high temperature thermometers.
• Gallium salts such as gallium citrate and gallium nitrate are used in medical imaging as radiocontrast agents.

Substitutes and Alternative Sources of Gallium

Silicon is being used for GaAs in solar cell applications. Gallium deposits are not going to run short in foreseeable future, but zinc deposits, as alternative sources, may sometime in future become important when easily accessible sources are used up.

Note:- Gallium arsenide circuits are very specialized and do not have a substitute.

Occurrences of Gallium

• France (leading refiner of gallium metal)
• Russia
• Canada
• Kazakhastan