Which of the following has maximum number of unpaired electrons:

Options

A. `Fe^(2+)`
B. `Fe^(3+)`
C. `Se^(3+)`
D. `Cu^(2+)`

Explanation

`Fe^(+3)=[Ar]_(18)3d^(5)` (5 unpaired electron)
`Fe^(+2)=[Ar]_(18)3d^(6)`(4 unpaired electron)
`Se^(+3)=[Ar]_(18)` (0 unpaired electron)
`Cu^(+2)=[Ar]_(18)3d^(9)` (1 unpaired electron)