The bond dissociation energy (BDE) of F 2 ( 158 kJ / mol ) is significantly lower than Cl 2 ( 242 kJ / mol ) . Which of the following factors provides the most accurate multi-concept explanation f

Question

The bond dissociation energy (BDE) of F 2 ​ ( 158 kJ / mol ) is significantly lower than Cl 2 ​ ( 242 kJ / mol ) . Which of the following factors provides the most accurate multi-concept explanation for this anomaly?

TestHub · Accepted Answer

Question Explanation: Explains the anomalous low bond energy of Fluorine due to electron density. Concept:

Inter-electronic Repulsion in Halogens

Solution:

Fluorine is a very small atom with a short bond length. The high density of lone pairs on each Fluorine atom leads to significant lone pair-lone pair (LP-LP) repulsion at such close proximity. This repulsive force offsets the energy gained from orbital overlap, making the $F - F$ bond much weaker than the $Cl - Cl$ bond, where larger atoms keep lone pairs further apart. Bond Energy: $Cl_{2} > Br_{2} > F_{2} > I_{2}$ (Anomalous order).

Final Answer: Lone pair-lone pair (LP - LP) repulsion in the very short F - F bond dominates over the gain in overlap energy.

Chemistry - CHEMICAL BONDING Question with Solution | TestHub

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Doubts & Discussion

JEE Main 2027 (Class 12+)