Which one of the following orders is correct for the bond dissociation enthalpy of halogen molecules ?
Bond lengths of halogens are in the order : F2 < Cl2 < Br2 < I2.
Bond energies are expected in the order :F2 > Cl2 > Br2 > Cl2.
But the experimental bond enthalpies are :Cl2 > Br2 > F2 > I2 Bond enthalpy of F2 is very less, because lone pair - lone pair repulsions are appreciable in F2 as the bond length is small in F2. 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 of fluorine.