Question

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

Options

• Br₂ > I₂ > F₂ > Cl₂

• F₂ > Cl₂ > Br₂ > l₂

• I₂ > Br₂ > Cl₂ > F₂

• Cl₂ > Br₂ > F₂ > I₂

Answer 1

Cl₂ > Br₂ > F₂ > I₂

Explanation:

Bond dissociation enthalpy generally decreases down the group due to increasing atomic size. However, F₂ is an exception due to strong lone pair repulsions in the small F-F bond, which weakens it. Hence, Cl₂ has the highest bond energy among halogens, followed by Br₂, then F₂, and least in I₂.