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 and 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 O2ion will be:

Bond order of = O2- =1/2 (8-5) = 1.5

Thus, the bond order of ion is  O2- = 1.5.