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Question #44264

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The Question

The successive ionization enthalpies ( $IE_1, IE_2, IE_3$ ) of 3d transition metals are governed by the effective nuclear charge ( $Z_{eff}$ ), the screening effect of inner d-electrons, and the exchange energy of half-filled subshells. Based on these thermodynamic factors, select the correct combination of orders for the gas-phase ionization enthalpies of the given elements at 298 K.

Options

A.
$IE_1$ : $\text{V} < \text{Cr} < \text{Mn}$ ; $IE_2$ : $\text{V} < \text{Mn} < \text{Cr}$ ; $IE_3$ : $\text{Fe} < \text{Cr} < \text{Mn}$
B.
$IE_1$ : $\text{V} < \text{Mn} < \text{Cr}$ ; $IE_2$ : $\text{V} < \text{Cr} < \text{Mn}$ ; $IE_3$ : $\text{Cr} < \text{Fe} < \text{Mn}$
C.
$IE_1$ : $\text{V} < \text{Cr} < \text{Mn}$ ; $IE_2$ : $\text{V} < \text{Cr} < \text{Mn}$ ; $IE_3$ : $\text{Cr} < \text{Mn} < \text{Fe}$
D.
$IE_1$ : $\text{Cr} < \text{V} < \text{Mn}$ ; $IE_2$ : $\text{Mn} < \text{V} < \text{Cr}$ ; $IE_3$ : $\text{Fe} < \text{Mn} < \text{Cr}$

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Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Numerical_Precision

Improve calculation stamina and avoid rounding errors in high-stakes competitive examinations.

Concepts Behind This Question

Hund’s Rule of Maximum Multiplicity|Ionization Enthalpy (IE) Anomalies|Screening Effect in Inner Shells

Why This Question Is Tricky

Common Mistakes

This problem tests the 'Shifting Stability Peak' trap.

Students often erroneously apply Hund's rule to the neutral atom, assuming Cr has the highest $IE_1$ .

The trap lies in recognizing that the $3d^5$ stability peak shifts across the series depending on the ionization state: it dictates $IE_2$ for Cr and $IE_3$ for Mn.

Furthermore, the anomalous drop in $IE_3$ for Fe (due to achieving $3d^5$ ) perfectly counters the assumption that $Z_{eff}$ strictly dictates a monotonic increase.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Structure of Atom - Class 11 Part 1
Concept	Hund’s Rule of Maximum Multiplicity
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free