For the four successive transition elements (Cr, Mn, Fe, and Co), the stability of `+2` oxidation state will be there in which of the following order ?
`(At. Nos. Cr = 24, Mn = 25, Fe = 26, Co = 27)`

Options

A. Mn gt Fe gt Cr gt Co
B. Fe gt Mn gt Co gt Cr
C. Co gt Mn gt Fe gt Cr
D. Cr gt Mn gt Co gt Fe

Answer

A

Explanation

`Mn^(2+) (3d^5)` has highest stabilization due to half filled configuration. `Fe^(2+) (3d^6) ` is less stable because of one extra electron in half filled configuration. `Cr^(2+) (d^4)` has one vacant subshell and `Fe^(2+)` is more stabilized as compared to` Cr^(2+)` because of exchange energy. Correct corder: Mn > Fe > Cr > Co