Chemistry - Complete Pblock- Question with Solution | TestHub

Lower value of bond dissociation energy of fluorine is due to the high inter electronic repulsions between non-bonding electrons of the $2p$-orbital of small sized fluorine. As a result $\mathrm{F}-\mathrm{F}$ bond is weaker as comparison to $\mathrm{Cl}-\mathrm{Cl}$ and $\mathrm{Br}-\mathrm{Br}$ bonds. $$\begin{array}{lr}& \text{ Bond dissociation energy }\\ \mathrm{F}-\mathrm{F}& 38\mathrm{K}\mathrm{cal}/\mathrm{mole}\\ \mathrm{Cl}-\mathrm{Cl}& 57\mathrm{K}\mathrm{cal}/\mathrm{mole}\\ \mathrm{Br}-\mathrm{Br}& 45.5\mathrm{K}\mathrm{cal}/\mathrm{mole}\\ \mathrm{I}-\mathrm{I}& 35.6\mathrm{K}\mathrm{cal}/\mathrm{mole}\end{array}$$