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Element Fact
Rhenium was the last naturally occurring element to be identified, in 1925. It was so rare that only 1 g of the metal was extracted out of 660 kg of molybdenite ore.

Gallium, Ga

gallium sample

Atomic number: 31
Atomic mass: 69.723(1)
Natural abundance: 19 ppm
69Ga (68.925581) - 60.108%
71Ga (70.924705) - 39.892%

History and Production

Derived from Latin Gallia, meaning France. It was predicted as eka-aluminium by D.I. Mendeleev in 1870. It was later discovered by P.E. Lecoq de Boisbaudran in 1875 by means of spectroscopic which was shown as two new violet lines in the spectrum. He managed to isolate only 1g of the metal from hundreds of kilograms of zinc-blende ore. The metal is difficult to extract due to lack of major gallium-containing ores. It can be obtained as a byproduct in the manufacture of aluminium (Bauxite contains up to about 0.01% of Ga). Ultra pure element for semiconductor industry is obtained by further chemical treatment, followed by crystallization and zone refining. It is used in making transistors, laser diodes, light-emitting diodes (LEDs) and as a dopant for other semiconductors. It is also use in low-temperature solders and high-temperature liquid seals.

Physical Data

It is slivery-blue in appearance and has a very melting point that could exist as a liquid near to room temperature. It wets glass or porcelain and forms a mirror when it is painted on a glass. However, it does not wet graphite or teflon. It has one of the broadest liquid ranges of any metal with very low vapor pressure even at high temperatures. Pure solid metal fracture like a glass and expands about 3% when solidify. Gallium is often found as a trace element in bauxite, germanite and sphalerite.

Interatomic distance: 244.2 pm
Melting point: 29.76C
Boiling point: 2204C
Thermal conductivity/Wm-1K-1: 40.6 (27C)
Density/kgm-3: 5907 (20C), 6114 (m.p.)

Standard Thermodynamic Data (atomic gas)

Enthalpy of formation: 272 kJ/mol
Gibbs free energy of formation: 233.7 kJ/mol
Entropy: 169.0 J/mol K
Heat capacity: 25.3 J/mol K

Electronic data

Electronic configuration: [Ar] 3d10 4s2 4p1
Term symbol: 2P1/2
Electron affinity: 41.4887   Electronegativity (Pauline): 1.81
Ionization energy (first, second, third): 578.845, 1979.32, 2963.07 kJ/mol

Chemical properties

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