Which of the following has the highest bond dissociation enthalpy?

Options

A. `F_2`
B. `Br_2`
C. `Cl_2`
D. `I_2`

Answer

C

Explanation

The order of bond dissociation enthalpy is
`underset((242.6kJ mol^(-1)))(Cl-Clgt)underset((192.8))(Br-Brgt)underset((158.8))(F-Fgt)underset((151.1))(I-I)`
In spite of the smallest bond length, `F_2` molecule has abnormally low bond dissociation enthalpy on account of interelectronic repulsion between the lone pair on F atoms in `:overset(..)underset(..)F-underset(..)overset(..)F:` molecule.