MHT CET202619 April 2026Evening ShiftChemistryp Block Elements (Group 15, 16, 17 & 18)Actual
Which of the following is the correct decreasing order of bond dissociation enthalpy of halogens ?
Options
- AF ₂ > Cl ₂ > Br ₂ > I ₂
- BI ₂ > Br ₂ > Cl ₂ > F ₂
- CCl ₂ > Br ₂ > F ₂ > I ₂
- DBr ₂ > I ₂ > F ₂ > Cl ₂
Correct answer
C. Cl ₂ > Br ₂ > F ₂ > I ₂
Step-by-step solution
The bond dissociation enthalpy of halogens generally decreases down the group as the atomic size increases, which leads to less effective overlap of orbitals. However, the bond dissociation enthalpy of F ₂ is exceptionally lower than that of Cl ₂ and Br ₂ . This is due to the very small size of the fluorine atom, which results in strong interelectronic repulsions between the non-bonding electrons (lone pairs) on the two closely spaced fluorine atoms. The experimental values of bond dissociation enthalpies are appro