Question

Of the \( d^4 \) species, Cr\(^{2+}\) is strongly reducing while Mn\(^{3+}\) is strongly oxidizing.

Hint:

- Stable electronic configurations drive oxidation/reduction tendencies. - Cr\(^{2+}\) prefers oxidation to \( d^3 \), Mn\(^{3+}\) prefers reduction to \( d^5 \).

Answer 1

Step 1: Electronic Configurations - Chromium (Cr): \[ \text{Cr}^{2+} = [\text{Ar}] 3d^4 \] \[ \text{Cr}^{3+} = [\text{Ar}] 3d^3 \quad (\text{Stable t}_{2g}^3 \text{ configuration}) \]- Manganese (Mn): \[ \text{Mn}^{3+} = [\text{Ar}] 3d^4 \] \[ \text{Mn}^{2+} = [\text{Ar}] 3d^5 \quad (\text{Stable half-filled d}^5 \text{ configuration}) \]Step 2: Explanation - Cr\(^{2+}\) readily loses an electron to form the stable Cr\(^{3+}\) (\( d^3 \)) configuration, acting as a strong reducing agent. - Mn\(^{3+}\) readily gains an electron to form the stable Mn\(^{2+}\) (\( d^5 \)) configuration, acting as a strong oxidizing agent.