Which one of the following ions has electronic configuration `[Ar]3d^(6)` ? `(At. Nos. Mn = 25, Fe = 26, Co = 27, Ni = 28)`

Options

A. `Co^(3+)`
B. `Ni^(3+)`
C. `Mn^(3+)`
D. `Fe^(3+)`

Answer

A

Explanation

`""_27Co = [Ar] 3d^7 4s^2`
`Co^(3+) = [Ar] 3d^6`.