Before You Begin

Question #44269

Difficulty: 8/10 | 🟢 Free

The Question

A 3d-transition metal $M$ has exactly four unpaired electrons in its neutral ground state. An aqueous solution of $MCl_3$ is treated with excess $KCN$ to form an octahedral complex anion $X$ . The actual spin-only magnetic moment of $X$ is $\mu_{actual}$ .

If the ionization of $M$ to $M^{3+}$ strictly followed the decreasing order of $(n+l)$ values for electron removal (i.e., electrons from the subshell with the highest $(n+l)$ value are removed first), the predicted spin-only magnetic moment of $X$ would be $\mu_{hypothetical}$ .

Assuming the ligand field splitting affects only the d-orbitals, what are the values of $\mu_{actual}$ and $\mu_{hypothetical}$ respectively?

Options

A.
$1.73 \text{ BM}$ and $3.87 \text{ BM}$
B.
$5.92 \text{ BM}$ and $3.87 \text{ BM}$
C.
$1.73 \text{ BM}$ and $5.92 \text{ BM}$
D.
$5.92 \text{ BM}$ and $1.73 \text{ BM}$

Check Your Answer

Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Exception_Exposure

Learn to identify edge cases and boundary exceptions that JEE examiners hide in math problems.

Concepts Behind This Question

Energy of Subshells (n+l rule)|Variable Oxidation State Stability|Spin-Only Magnetic Moment

Why This Question Is Tricky

Common Mistakes

The question tests the fundamental difference between the Aufbau principle (filling order based on the $n+l$ rule) and the ionization process (removal order based on principal quantum number $n$ ).

Students often erroneously apply the $n+l$ rule for electron removal, assuming 3d electrons are removed before 4s electrons because 3d is filled after 4s.

This trap is combined with Crystal Field Theory (strong field vs weak field ligands) to ensure the student can correctly determine the electronic configuration and the resulting spin-only magnetic moment in both the actual and hypothetical scenarios.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Structure of Atom - Class 11 Part 1
Concept	Energy of Subshells (n+l rule)
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free