Which of the following is the correct order of bond dissociation enthalpy?

Options

A. `F_(2) gt Cl_(2) gt Br_(2) gt I`
B. `I_(2) gt Br_(2) gt Cl_(2) gt F_(2)`
C. `Cl_(2) gt Br_(2) gt F_(2) gt I_(2)`
D. `Br_(2) gt I_(2) gt F_(2) gt Cl_(2)`

Answer

3

Explanation

The `F-F` bond dissociation enthalpy is smaller than that of `Cl-Cl` and even smaller than that of `Br-Br` ,because `F` atom is very small (`64` pm) relative to `Cl` atom (`99` pm) and `Br` atom (`114` pm) and thus the electron-electron repulsions between the lone pairs of electrons are very large.