The coloured compound among the following in the solid state is-
1. \( \mathrm{Ag}_{2} \mathrm{SO}_{4} \)
2. \(\mathrm {C u F}_{2} \)
3. \(\mathrm {Zn F}_{2} \)
4. \(\mathrm{Cu}_{2} \mathrm{Cl}_{2} \)



Hint: If unpaired electron is present in the central atom then it will show coloured

Transition elements form coloured salt due to the presence of unpaired electrons.

In Ag2SO4, Ag oxidation state is +1. It is a d10 system, does not contains unpaired electron hence, does not show any colour.

In ZnF2 , Zn oxidation state is +2. It is a d10 system, does not contains unpaired electron hence, does not show any colour.

In Cu2Cl2, Cu oxidation state is +1. It is a d10 system, does not contains unpaired electron hence, does not show any colour.

In CuF2, Cu oxidation state is +2. It is a d9 system, and contains one unpaired electron hence, CuF2, is coloured in solid state.