d and f Block Elements Part 2

Sc+3 and Zn+2 are colourless as they contain no unpaired electron. Whereas the transition metal ions Cu+2,Ti+3,V+2 and Mn+2 are coloured as they contain unpaired electrons.
The unpaired electron from lower energy d orbital gets excited to a higher energy d orbital on absorbing light of frequency which lies in visible region. The colour complementary to light absorbed is observed.