`Zn^(2+)` salt are white while `Cu^(2+)` salts are blue. Assign reason.

Explanation

The `Zn^(2+)` ion has all filled orbitals whereas `Cu^(2+)` ion ( `3d^(9)` configuration ) has one half filled 3d-orbitals. It has therefore, a tendency to form coloured ion in solution whereas `Zn^(2+)` has no such tendency. Thus, `Zn^(2+)` salts are white while those of `Cu^(2+)` ar blue.