Bond Order Formula

What is Bond order?

The bond order shows the number of chemical bonds present between a pair of atoms. For instance, the bond order of diatomic nitrogen N≡N is 3 and bond order between the carbon atoms in H-H≡C-H is also three. The bond order describes the stability of the bond.The molecular orbital provides an easy understanding of the concept of the bond order of a chemical bond. It quantifies the degree of covalent bonds between the atoms.


 How to calculate Bond order?

The Bond Order Formula can be defined as half of the difference between the number of electrons in bonding orbitals and antibonding orbitals.  


Nb is the number of bonding electrons

Na is the number of antibonding electrons


Example 1

Determine the bond order of C2 molecule.


Step 1. Write the electronic configuration of C2 molecule.

Electronic configuration of C2

= (σ1s)2 (σ*1s)22s)2(σ*2s)(π2px2 π2py2)


Step 2. From the above electronic configuration, put the values in the formula

Bond order = Nb – Na / 2


       = 6 – 2 / 2


                   = 2

The double bond in C2 consists of both π bonds due to the presence of four electrons in two π molecular orbitals. Therefore, the stability of C2 is very less.


Example 2

Determine the bond order of hydrogen molecule (H2).



Step 1. Write the electronic configuration of Hydrogen atom


The electronic configuration of hydrogen is (σ1s)2

Step 2. Put the values from the above electronic configuration in the bond order formula, we get

Bond order = 2 – 0 / 2

Therefore, bond order = 1

It means single covalent bond exist in H2 molecule, and diamagnetic since there is no unpaired electron.


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