Chemistry - Complete Pblock- Question with Solution | TestHub

Key Idea : Generally bond dissaciation energies decreases in a group. Bond dissaciation energy also decreases with repulsion. $\begin{array}{lcccc}X-X\text{ Bond }& \mathrm{F}-\mathrm{F}& \mathrm{Cl}-\mathrm{Cl}& \mathrm{Br}-\mathrm{Br}& \mathrm{I}-\mathrm{I}\\ \text{Bond length }(\mathring{A}))& 1.42& 1.99& 2.28& 2.67\\ \begin{array}{l}\text{Bond dissociation }\\ \text{energy }(\mathrm{kcal}/\mathrm{mol})\end{array}& 38& 57& 45.5& 35.6\end{array}$ In general the bond dissociation energy decreases as the bond length increases, but the bond dissociation energy of ${\mathrm{F}}_2$ is less than that of ${\mathrm{Cl}}_2$. It is due to greater interelectronic repulsions between the lone pair of electrons on the two bonded fluorine atoms. Hence, the order of bond dissociation energy is as : ${\mathrm{Cl}}_2>{\mathrm{Br}}_2>{\mathrm{F}}_2>{\mathrm{I}}_2$