Question

Give reason:
$Z{n}^{2+}$ salts are white $C{u}^{2+}$ salts are blue.

Answer 1

$Z{n}^{2+}$ salts are white as there is no unpaired $e^{-}$ present for transition, all $e^{-}s$ are paired.

$C{u}^{2+}$ salts are blue in colour as it contains $4s^{0}3d^9$ one unpaired $e^{-}$ which can undergo $d-d$ transition.