Why is `Cr^(2+)` reducing and `Mn^(3+)` oxidising when both have `d^(4)` configuration?

Explanation

`Cr^(3+) // Cr^(2+)` has a negative reduction potential or positive oxidation potential. Therefore, `Cr^(3+)` is most stable. Hence, `Cr^(2+)` can easily change to `Cr^(3+)` by the loss of an electron. Thus, `Cr^(2+)` acts as a strong reducing agent. On the other hand, `Mn^(3+)//Mn^(2+)` has large positive reduction potential. Hence, `Mn^(3+)` can be easily reduced and thus acts as a strong oxidising agent.`