Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion…

Assertion (A): $\text{Cr}^{2+}$ is reducing; $\text{Mn}^{3+}$ is oxidising — TRUE ✓

• $\text{Cr}^{2+}$ ($3d^4$) readily loses an electron to become $\text{Cr}^{3+}$ ($3d^3$, stable) → reducing agent
• $\text{Mn}^{3+}$ ($3d^4$) readily gains an electron to become $\text{Mn}^{2+}$ ($3d^5$, half-filled stable) → oxidising agent

Reason (R): Half-filled configuration has extra stability over incompletely filled — TRUE ✓

Is R the correct explanation of A? YES ✓

• $\text{Cr}^{2+}$ ($3d^4$) → $\text{Cr}^{3+}$ ($3d^3$): gains stability (not half-filled but $3d^3$ is stable due to exchange energy)
• $\text{Mn}^{3+}$ ($3d^4$) → $\text{Mn}^{2+}$ ($3d^5$): gains half-filled stability → strong driving force to oxidise

The extra stability of the half-filled $3d^5$ configuration directly explains why $\text{Mn}^{3+}$ is a strong oxidising agent.

Answer: Option (1) — Both true, R is correct explanation