Question 40
What is meant by the term bond order? Calculate the bond order of: N2, O2,O2+,and O2-.
Bond order is defined as the number of covalent bonds in a covalent molecule.It is equal to one half of the difference between the number of electrons in the bonding & antibonding molecular orbitals.
Bond order = [no of electrons in bonding MO – no of electrons in antibonding MO] / 2
BOND ORDER OF N2
Electronic configuration of N 
Number of bonding electrons = 10
Number of anti-bonding electrons = 4
Bond order of nitrogen molecule = 1/2 (10-4) = 3
Bond order of O2
Electronic configuration of O
Number of bonding electrons = 8
Number of anti-bonding electrons = 4
Bond order = 1/2 (8-4) =2
Hence, the bond order of oxygen molecule is 2.
Bond order of O2+
Electronic configuration of can be written as:
Bond order of O2+=1/2 (8-3)= 2.5
Thus, the bond order of O2+ is 2.5.
Bond order of O2-
The electronic configuration of O2- ion will be:
Bond order of = O2- =1/2 (8-5) = 1.5
Thus, the bond order of ion is O2- = 1.5.
