Question

What may be the stable oxidation state of the transition element with the following d-electron configuration in the ground state of their atoms: $3d^3,3d^5,3d^8$ and $3d^4$ ?

Answer 1

Stable oxidation states:
$3d^3$ : Vanadium $\left(3d^{3}4s^2\right)$ : oxidation states +2, +3, +4 and +5.
$3d^5$ : Chromium $\left(3d^{5}4s^1\right)$ : oxidation states +3, +4 and +6.
$3d^5$ : Manganese $\left(3d^{5}4s^5\right)$ : oxidation states (+2, +4, +6, +7).
$3d^8$ : Cobalt $\left(3d^{7}4s^2\right)$ : oxidation states +2, +3 (in complexes) (Co belongs to 9 group)
$3d^4$ : Such configuration does not exist in ground state.