Question

Oxidation number of AuCl4

Answer 1

Halogens always have an oxidation number of -1 unless they are combined with oxygen. Hydrogen is always either +1 or -1, depending on if its bonded to a metal or non-metal. Since the compound is neutral, the sum of the oxidation numbers must be zero. So, you've got 4 Cl (-1 x 4= -4) Then you're hydrogen will be +1, so your gold has to be +3 to make the compound neutral.