Q12 / 75 · JEE Main 2025 (4 Apr Shift 2) · Chemistry

The incorrect relationship in the following pairs in relation to ionisation enthalpies is :

  • A
    $\mathrm{Mn}^{+} \lt \mathrm{Cr}^{+}$
  • B
    $\mathrm{Mn}^{+} \lt \mathrm{Mn}^{2+}$
  • C
    $\mathrm{Fe}^{2+} \lt \mathrm{Fe}^{3+}$
  • Correct answer
    D
    $\mathrm{Mn}^{2+} \lt \mathrm{Fe}^{2+}$

Solution

$\mathrm{Mn}^{2+}:[\mathrm{Ar}] 3 \mathrm{~d}^5$
Half filled stability
More 1 E than $\mathrm{Fe}^{2+}$
$\mathrm{Fe}^{2+}:[\mathrm{Ar}] 3 \mathrm{~d}^6$

Hence, the correct answer is option: 'D'.

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