MCQ
The transition metal having highest $3^{\text {rd }}$ ionisation enthalpy is :
  • A
    $\mathrm{Cr}$
  •  $\mathrm{Mn}$
  • C
    $\mathrm{V}$
  • D
    $\mathrm{Fe}$

Answer

Correct option: B.
 $\mathrm{Mn}$
b
$3$rd Ionisation energy : [$NCERT$ Data]

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

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

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

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

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.

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