## Chemistry: Molecular Approach (4th Edition)

The electron configuration of Sc is $[Ar]4{{s}^{2}}3{{d}^{1}}.$ During the formation of $S{{c}^{3+}}$ it attains noble gas configuration and no free electrons are present for excitation, so it is colorless. The electron configuration of Ti is $[Ar]4{{s}^{2}}3{{d}^{2}}$. During the formation of $T{{i}^{3+}}$, its electron configuration becomes $[Ar]2{{d}^{1}}.$ It possesses a single electron that can be excited by the absorption of light, so it is colored.