(i) Ti3+ (3d1) has one unpaired electron in 3d sub-shell.
Sc3+ (3d0) does not have any unpaired electron.
Ti3+ in aqueous solution is coloured due to d-d transition but Sc3+ is colourless.
(ii) Cr2+ (3d4) is a strong reducing agent as it is easily oxidised to Cr3+ (3d3) which has a stable configuration due to half-filled t2g.
\(\underset{t_{2g}^{3}e_{g}^{1}} {Cr^{2+}} \rightarrow \underset{t_{2g}^{3}}{Cr^{3+}} +e\)
