i. Electronic configurations of Sc3+, Ti4+, V5+ are:
Sc3+: [Ar] 3d0 ; Ti4+: [Ar] 3d0 ; V5+: [Ar] 3d0
ii. The ions Sc3+, Ti4+ and V5+ have completely empty d-orbitals i.e., no unpaired electrons are present. Thus, their salts are colourless, as d-d transitions are not possible.