(i) Sc = [Ar] 3d14s2; Sc3+ = [Ar] ; it has no unpaired electron so diamagnetic
Cr = [Ar] 3d54s1; Cr3+ = [Ar]3d3; it has three unpaired electrons paramagnetic
(ii) V = [Ar] 3d34s2; Mn = [Ar]3d54s2 Thus V exhibit oxidation states of +2, +3, +4, +5 whereas Mn exhibit oxidation states of +2 to +7.
(iii) V4+ = [Ar] 3d1 → coloured V5+ = [Ar] → Colourless