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Question #44159

Difficulty: 8/10 | 🟢 Free

The Question

Consider the gaseous transition metal dimer $\ce{Cr2}$ . Assuming ideal Molecular Orbital Theory (MOT) for d-block dimers where all valence electrons participate in bonding, determine the formal bond order, its magnetic nature, and the number of $\delta$ -bonds present in its ground state.

Options

A.
6, \text{Diamagnetic}, 2
B.
5, \text{Paramagnetic}, 1
C.
4, \text{Diamagnetic}, 0
D.
0, \text{Paramagnetic}, 0

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

MOT and Magnetic Nature|Aufbau Principle Exceptions|Screening Effect in Inner Shells

Why This Question Is Tricky

Common Mistakes

This question tests the limits of Molecular Orbital Theory (MOT) by moving beyond the standard $s-p$ mixing seen in period 2 homonuclear diatomics (like $\ce{O2}$ or $\ce{N2}$ ).

Students often incorrectly assume that $d$ -electrons remain non-bonding or that the $3d^5 4s^1$ configuration will lead to a highly paramagnetic species due to Hund's rule in isolated atoms.

The hidden mechanism here is the profound inner-shell $d$ -orbital overlap that occurs in Group 6 dimers, leading to the formation of a sextuple bond (comprising $\sigma$ , $\pi$ , and $\delta$ interactions) and a completely diamagnetic ground state.

Failing to account for $\delta$ -bond formation from face-to-face $d$ -orbital overlap is a critical trap.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Chemical Bonding and Molecular Structure - Class 11 Part 1
Concept	MOT and Magnetic Nature
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free