` [T_i (H_2O)_6]^(3+ ) ` is coloured ,while `[Sc(H_2O)_6]^(3+) `is colourless -explain

Explanation

`Ti" in "[Ti(H_(2)O)^(6)]^(3+)" is in +3 oxidation state"`
`Sc" in "[Sc(H_(2)O)_(6)]^(3+)" is in +3 oxidation state."`
The outer electronic configuration of Sc, Ti and their trivalent ions are.
`{:(SC,:,3d^(1)4S^(2)""Ti,:,3d^(2)4S^(2)),(SC^(3+),:,3d^(0)""Ti^(3+),:,3d^(1)):}`
`Ti^(3+)` has one unpaired electron in 3d orbital and they undergoes d - d transition. This electron can be promoted to a higher energy level by light absorption. Therefore `[Ti(H_(2)O)^(6)]^(3+)` is coloured.
In the case of `[Sc(H_(2)O)_(6)]^(3+)`, there is no electron in 3d orbital of `Sc^(3+)`, hence there is no possibility of light absorbance. Therefore `[Sc(H_(2)O)_(6)]^(3+)` is colourless.