Gallium
. Gallium, symbol Ga, metallic element that remains in the liquid state over a wider range of temperatures than any other element. Gallium is in group 13 (or IIIa) of the periodic table ; its atomic number is 31. Gallium was discovered spectroscopically by the French chemist Paul Émile Lecoq de Boisbaudran in 1875; a year later he isolated the element in its metallic state. Gallium is blue-gray in color as a solid and silvery as a liquid. It is one of the few metals that are liquid near room temperature. It can be supercooled; like water, it expands upon freezing. The element is about 34th in order of abundance in Earth’s crust. Gallium melts at 30°C (86°F), boils at about 2403°C (about 4357°F), and has a specific gravity of 5.9; the atomic weight of the element is 69.72. Gallium occurs in small quantities in some varieties of zinc blende, bauxite, pyrite, magnetite, and kaolin. Gallium resembles aluminum in forming trivalent salts and oxides; it also forms a few monovalent and divalen