Write the different oxidation states of iron. Why +2 oxidation state of manganes is more stable ?
(Zof Mn =25).

Explanation

The different oxidiation states of iron are +2 and +3. The atomic number of Mn is
`25=1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)4s^(2)3d^(5)`
In + 2 oxidiation state, configuration will be
`1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)4s^(2)3d^(5)`
In +3 oxidation state, configuration will be
`1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)4s^(2)3d^(4)`
In `3d^(5)` configuration, Mn has half filled d-orbital and half filled and fully filed orbitals are more stable.

Also, shielding effect is small and electrons are strongly held by nucleus. The exchange energy of these electrons is very large. Thus +2 oxidation state is more stable.