Which of the following are coloured in aqueous solution ? Give reasons : `V^(3+), Cu^(+) , Sc^(3+) ,Fe^(3+)`

Explanation

`V^(3+)` and `Fe^(3+)` ions are coloured in aqueous solution. 3d metal ions having incompletely filled d-subshell can undergo d-d transition resulting in the formation of coloured complex. Among the given ions `V^(3+)(d^(2))` and `Fe^(3+)(d^(5))` have incompletely filled d-subshell [`Sc^(3+)` has no electron in d-orbital whereas in `cu^(+)` and d-orbital is completely filled] and hence they can only form coloured complex in aqueous solution .