4. d and f- block elements — Chemistry STD 12 Science — Question

$\mathrm{V}: 2833\ \mathrm{KJ} / \mathrm{mol}$

$\mathrm{Cr}: 2990\ \mathrm{KJ} / \mathrm{mol}$

$\mathrm{Mn}: 3260\ \mathrm{KJ} / \mathrm{mol}$

$\mathrm{Fe}: 2962\ \mathrm{KJ} / \mathrm{mol}$

alternative

$Mn$ : $3 d^5 4 s^2$

$\mathrm{Fe}: 3 \mathrm{~d}^6 4 \mathrm{~s}^2$

$\mathrm{Cr}: 3 \mathrm{~d}^5 4 \mathrm{~s}^1$

$V: 3 d^3 4 s^2$

So Mn has highest $3rd$ IE among all the given elements due to $d^5$ configuration.