Classification of Elements Part 1

Among halogens (F2,Cl2,Br2 and I2), bond dissociation enthalpy ( ∆‌diss ‌H∘ ) of I2, is minimum because of larger size of l-atom there is a steric repulsion between bonded l-atoms, which makes I- I bond weakest.
Whereas, smaller size and highest electronegativity of F-atom cause highest electron density on F-atom of F2 molecule. As a result, F−F bond becomes weaker due to electrostatic repulsion between bonded
F-atoms.
Thus, the order of ∆‌diss ‌H∘ (in kJmol−1 ) is