Question

Why do interhalogen compounds exhibit a decreasing bond dissociation energy as more of the same atoms are added (why does IF have a higher bond dissociation energy than IF3?)?

Answer 1

A strong bond is determined by a short bond length and a large bond dissociation energy. Hence IF have short bond which posses high dissociation energy. When 2 more fluorine added into that the bond between iodine and fluorine increases. if bond length increases polarity also will increase resulting dissociation energy will reduce.

(dissociate energy represents the dissociate the bond between 2 atoms . when the bond between 2 atoms increases dissociation energy will decrease)