Explain why `CuSO_4` is blue while `ZnSO_4` is white.

Explanation

In `CuSO_4` , the `Cu^(2+)` ion has `3d^9` configuration with one unpaired electron , so it is blue , But in `ZnSO_4` , the `Zn^(2+)` ion has `3d^10` configuration with no unpaired electron So it is white.