transition elements are 'd' block elements. `Cr^(2+)` and `Mn^(3+)` have `d^4` configuration. But `Cr^(2+)` is reducing and `Mn^(3+)` is oxidizing. Why?

Explanation

This is due to the extra stability of `Cr^(2+)` and `Mn^(2+)` ions. `{Cr^(3+)-d^3`configuration `[t_2^3g`, half-filled `t_(2g)` level] and `mn^(2+)-d^5` configuration, half-filled configuration}`Cr^(+2)rarrunderset(("stable"))(Cr^+3)+"le"^-`Act as reducmg agent `Mn^(+3)+"le"^(-)rarrunderset(("stable"))(Mn^(+2)`Act as oxidising agent.