The transition metal having highest $3^{\text {rd }}$ ionisation enthalpy is :

JEE Main · 2024 · 01 Feb 2024 · Shift 2 · d and f Block Elements

The transition metal having highest

3^{rd}

ionisation enthalpy is :

(A)Cr
(B)Mn✓ Correct
(C)V
(D)Fe

Answer: (B)

Solution

After two electrons are removed, the dications have configurations

V^{2 +} : 3 d^{3}

C r^{2 +} : 3 d^{4}

M n^{2 +} : 3 d^{5}

F e^{2 +} : 3 d^{6}

M n^{2 +}

holds the extra-stable, exchange-energy-maximised half-filled

3 d^{5}

configuration, so pulling out a third electron from it means disrupting that stability, which demands the most energy. Manganese therefore has the highest third ionisation enthalpy among the four.

JEE Main · 2024 · 01 Feb 2024 · Shift 2 · Single correct option

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