What is the order of bond enthalpies of halogens? Why is it not opposite to that of bond lengths?

Explanation

Bond lengths of halogens are in the order
`F_(2)ltCl_(2)ltBr_(2)ltI_(2)`.
Bond energies are expected in the order :
`Cl_(2)gtBr_(2)gtF_(2)gtI_(2)`
Bond enthalpy of `F_(2)` is very less, because lone pair-lone pair repulsions are appreciable in `F_(2)` the bond length is small in `F_(2)`. It was also thought, though not appropriate, that F-F bond is weak as multiple bond is not possible with no d-orbitals in the valence shell fo fluorine.
According to Mulliken, the high bond dissociattion energies of `Cl_(2),Br_(2) and I_(2)` are due to multiple bond formed by `dpi-ppi` combinations or overlapping may be possible.