Question

Out of Ag2SO4,CuF2,MgF2 & CuCl which compound will be coloured and why?

Answer 1

If we considered CuF2 the oxidation state of Cu is 2+

Cu : [Ar] 3d10 4S1
Cu2+ : [Ar] 3d9

There is one unpaired electron. This electron implants colour to the compound. If all the electrons are paired up, the compound will not be colored.