Predic which of the following will coloured in aqueous solution `Ti^(2+) , V^(3+) Sc^(4+) Cu^(+) ,Sc^(3+) ,Fe^(3+) ,Ni^(2+) ` and `Co^(3+)`

Explanation

(I ) Only the ions that have unpaired electrons in d- orbital and in which d- d transition is possible will be coloured.
(ii) The ions in which d - orbitals are empty or completely filled will be colourless as no d-d transition is possible those configuratin
From the above ions , it can be easily observed that only `Sc^(3+)` has an empty d- orbital and `Cu^(+)` has completely filled d- orbital.
(iv) All other ions except `Sc^(3+)` and `Cu^(+)` will be coloured in aqueous solution because of d-d transition.