Gallium is a chemical element with the symbol Ga and atomic number 31. Discovered by the French chemist Paul-Émile Lecoq de Boisbaudran in 1875, gallium is in group 13 of the periodic table and is similar to the other metals of the group (aluminium, indium, and thallium).

Elemental gallium is a relatively soft, silvery metal at standard temperature and pressure. In its liquid state, it becomes silvery white. If enough force is applied, solid gallium may fracture conchoidally. Since its discovery in 1875, gallium has widely been used to make alloys with low melting points. It is also used in semiconductors, as a dopant in semiconductor substrates.

The melting point of gallium is used as a temperature reference point. Gallium alloys are used in thermometers as a non-toxic and environmentally friendly alternative to mercury, and can withstand higher temperatures than mercury. An even lower melting point of −19 °C (−2 °F), well below the freezing point of water, is claimed for the alloy galinstan (62–⁠95% gallium, 5–⁠22% indium, and 0–⁠16% tin by weight), but that may be the freezing point with the effect of supercooling.

Gallium does not occur as a free element in nature, but as gallium(III) compounds in trace amounts in zinc ores (such as sphalerite) and in bauxite. Elemental gallium is a liquid at temperatures greater than 29. 76 °C (85. 57 °F), and will melt in a person's hands at normal human body temperature of 37. 0 °C (98. 6 °F).

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 is considered a technology-critical element by the United States National Library of Medicine and Frontiers Media. Gallium has no known natural role in biology. Gallium(III) behaves in a similar manner to ferric salts in biological systems and has been used in some medical applications, including pharmaceuticals and radiopharmaceuticals.

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Atomic properties

Standard atomic weight69.723 ±0.001
Atomic mass69.7231 u

Atomic radii

Radius (empirical)135 pm
Radius (calculated)136 pm
Covalent radius122 ±3 pm
Van der Waals radius187 pm

Atomic shell

Electron configurationAr 3d10 4s2 4p1
Ionization energy(1st) 5.999302 eV
(2nd) 20.51514 eV
(3rd) 30.72576 eV
(4th) 63.241 eV
(5th) 86.01 eV
Shell model

Physical properties

Density5.904 g·cm−3
Molar volume1.18·10-5 m3·mol−1
Speed of sound2,740 m·s−1 (293.1 K)


Melting point302.9 K
Boiling point2,673 K
Liquid range2,370 K
Transition temperature1.08 K


Melting enthalpy5.59 kJ·mol-1
Enthalpy of vaporization256 kJ·mol-1
Binding energy277 kJ·mol-1

Heat and conductivity

Specific heat capacity371 J·kg−1·K−1
Thermal conductivity29 W·m-1·K-1
Expansion coefficient1.2·10-4 K-1


Mohs hardness1.5
Brinell hardness60 NM·m-2

Electrical properties

Electrical conductivity7.14·106 S·m-1
Resistance1.4·10-7 Ωm


Magnetic susceptibility-2.16·10-5 cm3·mol−1 (290 K)

Chemical properties

Oxidation state3
Standard potential-0.53 V (Ga3+ + 3e- → Ga)


Pauling scale1.81
Sanderson scale2.42
Allred-Rochow scale1.82
Mulliken scale2.01
Allen scale1.756
Ghosh-Gupta scale4.663 eV
Boyd-Edgecombe scale1.75
Nagle scale1.56
Pearson absolute negativity3.2 eV

Other properties

Natural occurrenceprimordial
Crystal structureOrthorhombic
Goldschmidt Classificationchalcophile
Superconductorwith transition tempperature (solid body, normal pressure)
Price/kg148 USD

Natural abundances

10 ppb ≈ 1·1011 M☉
40 ppb ≈ 7.95·1010 Mt
7,800 ppb ≈ 7.8 g
Earth’s crust
19,000 ppb ≈ 526,000 Mt
0.03 ppb ≈ 41.1 kt
Flowing water
0.15 ppb ≈ 2.4 kt