Gallium
Symbol: Ga
Atomic Number: 31
Atomic Mass: 69.723 amu (atomic mass units)
Melting Point: 29.78 C (302.93 K, 85.604004 F)
Boiling Point: 2403.0 C (2676.15 K, 4357.4 F)
Number of Protons: 31
Number of Electrons: 31
Number of Neutrons: 39
Classification: Metallic
Crystal Structure: Orthorhombic
Density @ 293 K: 5.907 grams per cubic centimeter
Color: White/Silver
In 1871 Mendeleev predicted the existence of element 31 based of a gap in his periodic table. He suggested the name “eka-aluminium” with the symbol “Ea” for this element. Mendeleev also made predictions as to its likely properties. When element 31 was discovered many of his predicted properties were found to be correct.
Gallium was first observed spectroscopically by the French chemist Paul-Emile Lecoq de Boisbaudran in 1875. He managed to produce the pure element later in the same year by using electrolysis on a solution of gallium hydroxide. The name may be derived from either of two Latin words “Gallia” for France, or “gallus” for cockerel and relating to the surname of its discoverer.
The metal fractures with a conchoidal fracture which is similar to that seen in glass. In its pure form gallium is only very slowly attacked by mineral acids.
The metal is liquid at just above room temperature. It also has one of the largest liquid ranges of any metal. The liquid metal can supercool below its freezing point so seeding it sometimes necessary to start solidification. Even at high temperatures gallium has a very low vapor pressure.
Another property of this element is that it expands 3.1% when it solidifies. For this reason the liquid form of the element should not be stored in glass bottles as they can break when the metal expands.
Gallium has two naturally occurring stable isotopes. These are gallium-69 (60.108%) and gallium-71 (39.892%). Over thirty unstable isotopes of gallium have been produced.
The element is found in trace amounts in the mineral ores diaspore, sphalerite, germanite and bauxite. Flue dusts produced by burning coal can contain up to 1.5% gallium.
Gallium and some of its compounds has a number of scientific and industrial uses.
* Its low melting point and large liquid range has made gallium useful in the production of high temperature thermometers.
* Gallium can wet glass and porcelain. When painted on glass it produces a brilliant mirror.
* It is used to dope semiconductors.
* Gallium is used in the production of solid state transistors and light emitting diodes.
* It is used to produce low melting point alloys with a number of metals.
* Gallium arsenide can produce coherent (laser) light directly from electricity.
* Impure magnesium gallate is used in the production of ultra violet activated phosphors.
* Gallium trichloride is used in large quantities at the Gallium neutrino Observatory in Italy where neutrino particles produced by nuclear fission in the sun are being studied.
