Gallium, atomic no. 31, symbol Ga, weight at 69.723, is a very important semiconductor.
Gallium has the second largest liquid range of any element and is one of the few metals that is liquid near room temperature, melting in the hand. Gallium liquid clings to or wets glass and similar surfaces. Gallium also has the unusual property that (like water) it expands as it freezes.
Low melting gallium alloys are used in some medical thermometers as non-toxic substitutes for mercury. Gallium arsenide is used in semiconductor production mainly for laser diodes, light-emitting diodes and solar panels. It is also used to create brilliant mirrors.