Chemistry - Complete d-block Question with Solution | TestHub

${\mathrm{Ti}}^{3+}=1s^2,2s^{2}2p^6,3s^{2}3p^{6}3d^1$ $${\mathrm{Sc}}^{3+}=1s^2,2s^{2}2p^6,3s^{2}3p^6$$ (Unpaired electron absent in d-orbital) $${\mathrm{Cu}}^{+}=1s^2,2s^{2}2p^6,3s^{2}3p^{6}3d^{10}$$ Thus, ${\mathrm{Cu}}^{+}$has completely occupied $d$-orbital. Hence, in the above ions, ${\mathrm{Ni}}^{2+}$ and ${\mathrm{Ti}}^{3+}$ ions are coloured ions in the aqueous solution because of the presence of unpaired electrons in the $d$-subshell. Related Theory Whenever light falls on the transition element compounds electrons absorb energy and excite. When these electrons de-excite they release visible light wavelength. That's why transition element compounds exhibit colour.