Why are `Mn^(2+)` compounds more stable than `Fe^(2+)` towards oxidation to their +3 state ?

Explanation

Electronic configuration of `Mn^(2+)` is `3d^(5)` which is half-filled and hence stable. Therefore, third ionisation enthalpy is very high, i.e., third electron cannot be lost easily as it would affect the stability of `3d^(5)` configuration. In case of `Fe^(2+)`, electronic configuration is `3d^(6)`. Hence, it can lose one electron easily to give the stable configuration `3d^(5)`.