One half the difference between the number of electrons present in the bonding and the anti-bonding orbitals is bond order
Bond order (B.O) =1/2(Nb−Na)
Bond order of H2−
Total number of electrons =2+1=3
Molecular orbital electrons is configuration
Bond order =1/2(2−1)=21
bond order of H2= 1/2 (2-0) = 1,
which means H2has only one bond. The antibonding orbital is empty.