The exhibition of various oxidation states by an element is also...

Elements which have only s-electrons in the valence shell do not show more than one oxidation state. Thus, element with $3 s^1$ as outer electronic configuration shows only one oxidation state of +1. Transition element such as elements (b), (c) having incompletely filled $d$-orbitals in the penultimate shell show variable oxidation states. Thus, element with outer electronic configuration as $3 d^1 4 s^2$ shows variable oxidation states of +2 and +3 and the element with outer electronic configuration as $3 d^2 4 s^2$ shows variable oxidation states of $+2,+3$ and +4. p-Block elements also show variable oxidation states due to a number of reason such as involvement of $d$-orbitals and inert pair effect e.g., element (d) with $3 s^2 3 p^3$ as (i.e., P) as the outer electronic configuration shows variable oxidation states of +3 and +5 due to involvement of $d$-orbitals.