The standard electrode potential () for the couple is highly positive (), whereas it is heavily nega — d and f Block Elements Chemistry Question

💡 Solution & Explanation

$Mn^{3+}$ ($d^4$) is a strong oxidizing agent because gaining an electron yields the exceptionally stable half-filled $d^5$ state. Conversely, $Cr^{3+}$ already possesses a highly stable $t_{2g}^3$ state in an aqueous octahedral field, so it resists gaining an electron to become $Cr^{2+}$ ($d^4$).