1. I₂ > Br₂ > Cl₂ > F₂ 2. Cl₂ > Br₂ > F₂ > I₂ 3. Br₂ > I₂ > F₂ > Cl₂ 4. F₂ > Cl₂ > Br₂ > I₂

Answer: 2. Cl₂ > Br₂ > F₂ > I₂ Key idea: bond dissociation enthalpy generally falls down group 17 (bigger atoms, longer bonds), but F₂ is unusually low because of strong lone pair repulsion in the short F-F bond. Values (kJ/mol): Cl₂ 242, Br₂ 193, F₂ 158, I₂ 151. So Cl₂>Br₂>F₂>I₂ , option 2.

Topic: General trends, Group 17 and 18· p-Block Elements

Which one of the following orders is correct for the bond dissociation enthalpy of halogen molecules ?

1. \(I_2 > Br_2 > Cl_2 > F_2\)

2. \(Cl_2 > Br_2 > F_2 > I_2\)

3. \(Br_2 > I_2 > F_2 > Cl_2\)

4. \(F_2 > Cl_2 > Br_2 > I_2\)

Doubtly Asked 30 Oct 2026 NEET UG 2016 Phase 1 Practice test neet Save WhatsApp Report

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Answer: 2. \(Cl_2 > Br_2 > F_2 > I_2\)

Key idea: bond dissociation enthalpy generally falls down group 17 (bigger atoms, longer bonds), but \(\mathrm{F_2}\) is unusually low because of strong lone pair repulsion in the short F-F bond.

Values (kJ/mol): \(\mathrm{Cl_2}\) 242, \(\mathrm{Br_2}\) 193, \(\mathrm{F_2}\) 158, \(\mathrm{I_2}\) 151. So \(\mathrm{Cl_2>Br_2>F_2>I_2}\), option 2.

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

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Which one of the following orders is correct for the bond dissociation enthalpy of halogen molecules ?

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