Which of the following set has all the coloured ions ?

Options

A. `Cu^(+),Cu^(2+),Ni^(2+)`
B. `Cu^(2+),Co^(2+),Sc^(3+)`
C. `Cu^(2+),Fe^(2+),Co^(2+)`
D. `Na^(+),Mg^(2+),Al^(3+)`

Answer

C

Explanation

In set `Cu^(2+),Fe^(2+),Co^(2+)`, all the ions have unpaired d-electrons. Hence, they are all coloured ions.
`Cu^(2+)rarr[Ar]3d^(9)4s^(0)`
`Fe^(2+)rarr[Ar]3d^(6)4s^(0)`
`Co^(2+)rarr[Ar]3d^(7)4s^(0).`