is gallium ionic or covalent?

Answer 1

The salts and oxide of gallium have a lot of ionic character. However, as Linus Pauling calculated, every ionic compound has covalent character. In particular, in the 19th century, chemists wanted to determine the atomic weight of gallium. They tried to use the law of Dulong and Petite, by which the atomic weight times the heat capacity of the metal was equal to 6.9. They got an inexact figure for the valence (oxidation number) of gallium. They resorted to making the gallium ammonium sulfate. That compound could either be Ga 2+, Ga(NH4)2(SO4)2, a schoenite, or Ga 3+, GaNH4(SO4)2, an alum. According to the crystallization habit of the compound, it was an alum and not a schoenite, and so the oxidation state of Ga was3+ and not 2+.