Gallium has three valence electrons. One can find this by looking at the electron configuration, which is Ga:[Ar] 4s2 3d10 4p1. In a chemical reaction, one can lose the electrons in the 4s and 4p subshell, and the total number of electrons in these subshells is three.
Valence shells, which are the outermost orbital shells of any atom, contain the valence electrons. These are the electrons that an atom can lose or acquire in a chemical reaction.
Gallium is a metal element. Its atomic number is 31, and its atomic weight is 69.72. On the periodic table, gallium is a member of Group 13. Although gallium is not present in pure form in nature, some ores that contain it are germanite and sphalerite. One application for gallium is in semiconductors.