\(\mathrm{V}: 2833 \mathrm{KJ} / \mathrm{mol}\)

\(\mathrm{Cr}: 2990 \mathrm{KJ} / \mathrm{mol}\)

\(\mathrm{Mn}: 3260 \mathrm{KJ} / \mathrm{mol}\)

\(\mathrm{Fe}: 2962 \mathrm{KJ} / \mathrm{mol}\)

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.