Compare the relative stability of +2 oxidation states in aqueous solutions for the metals having in their atoms the outer electron configurations, `3d^(3) 4s^(2), 3d^(6) 4s^(2)` and `3d^(5) 4s^(2)`.

Explanation

The relative stability of +2 oxidation states for the metals is given below:
`Mn^(2+)(3d^(5))gt V^(2+)(3d^(3))gt Fe^(2+)(3d^(6))`
`3d^(5)4s^(2)gt 3d^(3)4s^(2)gt 3d^(6)4s^(2)`
It is because `Mn^(2+)` has half-filled d-orbitals, therefore it is more stable. `Fe^(2+)` does not have half-filled d-orbitals. `V^(2+)` is more stable than `Fe^(2+)` because it has `t_(2g)` orbitals which is half-filled and thus more stable.