Question

Which of the $3d$ series of the transition metals exhibits the largest number of oxidation states and why?

Answer 1

In $3d$ series of transition metals manganese shows largest number of oxidation states. The outer electronic configuration of manganese is $3d^{5}4s^2$. As $3d$ and $4s$ are close in energy, it has maximum number of electrons to lose or share because it has highest number of unpaired electrons in its $d$-orbitals.

So, by removing its all electrons we get different oxidation states. It shows oxidation states from $+2$ to $+7$ which is the maximum number.

$\text{Example:}Mn{O}_2(+4),Mn{O}_4^{-}(+7),MnO(+2),$ etc.