Question

Give reason: $C{u}^{+}$ ion is colorless but $C{u}^{2+}$ ion is colored. Explain.

Answer 1

$C{u}^{+}$ ion has an electronic configuration $3d^{10}$ whereas $C{u}^{2+}$ ion has an electronic configuration $3d^9$. Hence an unpaired electron is present in $C{u}^{2+}$ which makes electronic transition feasible in case of $C{u}^{2+}$ ion, thus imparting color. Due to lack of unpaired electrons, $C{u}^{+}$ is colorless