JAMB Chemistry 2013 Paper

Concept:Transition metal ions appear colored because of electronic transitions within their partially filled $\mathrm{d}$-orbitals.Explanation:In transition metals, the $\mathrm{d}$-orbitals are not completely filled in their ions.When visible light falls on the ion, electrons absorb energy and jump between the split $\mathrm{d}$-orbitals.This $\mathrm{d}$–$\mathrm{d}$ transition absorbs certain wavelengths of visible light, and the remaining light is seen as color.Answer:D. $\mathrm{d}$-orbital