Which of the following statements is correct regarding the stability of oxidation states in the first transition series?

Solution

1. The ${\text{Mn}}^{2+}$ ion has a $d^5$ electronic configuration, which is extra stable due to half-filled subshell symmetry.
2. The ${\text{Mn}}^{3+}$ ion has a $d^4$ configuration and tends to gain an electron to reach the stable $d^5$ state.
3. Therefore, ${\text{Mn}}^{2+}$ is significantly more stable than ${\text{Mn}}^{3+}$ in aqueous media.
4. Hence the answer is (A).