This element was discovered in 1875 by P. Lecoq de Boisbaudran in Paris. The name comes from the Latin designation of France (Gallia) or from the translation of Lecoq (gallus).

Ionization energies
GaI 6.0 eV, GaII 20.5 eV, GaIII 30.7 eV, GaIV 64.2 eV.

Absorption lines of GaI
The equivalent width of GaI 4172(1) in the sun is 0.042. GaI is also seen in oneM 2III star (Davis 1947) and in long-period variables of types M and S (Merrill and Lowen 1953).

Emission lines of GaI
The 4172 line of Ga I is present in emission toward minimum light in long-period variables (Merrill and Lowen 1953).

Absorption lines of GaII
The equivalent width of GaII 4256 in B 8V stars is 0.005.

Behavior in non-normal stars
GaII was first detected by Bidelman and Corliss (1966) in Bp stars of the Hg-Mn subgroup. It is enhanced in almost all objects of this type. Typically W(4256) = 0.090 (Kodaira and Takada 1978).

The ultraviolet GaII resonance line 1414 is strong in some Hg-Mn stars (Jacobs and Dworetsky 1981), with W up to 1.30.Jaschek andJaschek (1987a) have introduced a subgroup called 'ultraviolet gallium stars' characterized by a strong 1414 line. Objects of this group may belong in the photographic region to a variety of subgroups (Si, He-weak, Hg-Mn, etc.).

Takada-Hidai et al. (1986) investigated in detail the ultraviolet lines of GaII (1414) and GaIII (1495) in hot Bp stars. They found GaIII lines to be strong in Bp stars of the same subgroups as those in which Ga II lines are enhanced, with W(1414) up to 1.86 in Hg-Mn stars and W(1495) up to 0.067. For these spectral types (B 5-A0) the Ga lines are below the detection limit (which can be assumed to be 0.002 Åin normal stars. Lanz et al. (1993) have observed the red GaII lines (6334, 6419 and 6456) in Ap stars, finding that GaII is enhanced both in magnetic and non-magnetic stars. Typically W(6334) < 0.11.

Ga has two stable isotopes - Ga69 and Ga71 - and 12 short-lived ones. In the solar system, Ga69 is 60% of all Ga and Ga71 is 40%.

The two stable Ga isotopes are produced by s, r or nuclear statistical equilibrium processes.

Published in "The Behavior of Chemical Elements in Stars", Carlos Jaschek and Mercedes Jaschek, 1995, Cambridge University Press.