Chemistry - Complete d-block Question with Solution | TestHub

Cuprous ions $\left({\mathrm{Cu}}^{+}\right)$is colourless because it has no unpaired electrons in the $3d$ sub-shell as it has $3d^{10}$ configuration. The cupric ion $\left({\mathrm{Cu}}^{++}\right)$has one unpaired electron as it has configuration $3d^9$. By absorbing the visible light, the unpaired electron can migrate from one set of $d$-orbitals to another under the applied field of water molecules. Hence, cupric ion $\left({\mathrm{Cu}}^{++}\right)$in aqueous solution shows blue colour.