Explain why `Fe^(3+)` is more stable than `Fe^(2+)` ion.

Explanation

Atomic number of Fe-atom=26 and its electronic configuration: `1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)3d^(6)4s^(2)`
`therefore`Electronic config. Of `Fe^(2+):1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)3d^(6)`
and electronic config. Of `Fe^(3+):1s^(2)2s^(2)2p^(6)3s^(2)2p^(6)3d^(5)`
We know that the electronic configuration of half-filled or fully filled subshells are more stable compared to others. now, the 3d-subshells are more stable compared to other. now, the 3d-subshell of `Fe^(3+)` ion is exactly half-filled and hence `Fe^(3+)` is more stable than `Fe^(2+)`.