JEE Main 2025 Apr 4 Shift 2, Chemistry Q2: d-Block Elements

Configurations of the relevant ions:

$M{n}^{2+}:[Ar]3d^5$   (half-filled, extra stable)

$F{e}^{2+}:[Ar]3d^6$

Removing an electron from $M{n}^{2+}$ disrupts a half-filled $d^5$ shell, so its ionisation enthalpy is higher than that of $F{e}^{2+}$.

$\therefore$ $M{n}^{2+}>F{e}^{2+}$ (in IE), and the listed relation $M{n}^{2+}<F{e}^{2+}$ is the incorrect one.