The bond dissociation energy is highest for

We need to determine which diatomic halogen molecule has the highest bond dissociation energy.

Bond dissociation energies of halogens:

The bond dissociation energies follow the general trend:

$$\text{Cl}_2 (242 \text{ kJ/mol}) > \text{Br}_2 (193 \text{ kJ/mol}) > \text{F}_2 (159 \text{ kJ/mol}) > \text{I}_2 (151 \text{ kJ/mol})$$

Explanation:

Generally, bond dissociation energy decreases as we go down the group due to increasing atomic size and decreasing orbital overlap. However, $$\text{F}_2$$ is an exception — it has an anomalously low bond dissociation energy because the small size of fluorine atoms leads to strong lone pair-lone pair repulsion between the closely placed non-bonding electrons.

Therefore, $$\text{Cl}_2$$ has the highest bond dissociation energy among the halogens.

The correct answer is Option 1: Cl$$_2$$.