The bond order of the ClF molecule have to get from the molecular orbital energy level diagram.
The bond order in ClF is 1 with 2 pairs of lone pair of electron on both the atom.
The energy level diagram of the molecule is shown in the figure.
There are 2 electrons in the bonding orbital i.e. σp orbital and no electron in its corresponding anti bonding orbital.
Now we know the bond order of a molecule is [tex]\frac{1}{2}[/tex] [Electrons in boding orbital - electrons in anti bonding orbital]
Thus in this case [tex]\frac{1}{2}[/tex] [2-0] = 1.
There remains 2 pairs of non bonding electrons on Cl and F atom as shown in the diagram. The energy level of 2p valence electron of F atom will be lower than the 3p valence electron of Cl atom.
