In both O2 (oxygen molecule) and N2 (nitrogen molecule), the bond order for the nitrogen atom is 3.
Bond order is a measure of the number of chemical bonds between two atoms in a molecule. It provides insight into the stability and strength of the bond. The bond order is calculated by taking the difference between the number of bonding electrons and the number of antibonding electrons, divided by 2.
In the case of O2, each oxygen atom contributes six electrons (two from each of the three oxygen-oxygen bonds) to the bonding molecular orbitals. There are no antibonding electrons. Therefore, the bond order of each oxygen-oxygen bond is:
Bond order = (Number of bonding electrons - Number of antibonding electrons) / 2 = (6 - 0) / 2 = 3 / 2 = 1.5
For N2, each nitrogen atom contributes five electrons (one from each of the three nitrogen-nitrogen bonds and two from a lone pair) to the bonding molecular orbitals. Again, there are no antibonding electrons. Thus, the bond order of each nitrogen-nitrogen bond is:
Bond order = (Number of bonding electrons - Number of antibonding electrons) / 2 = (5 - 0) / 2 = 5 / 2 = 2.5
Since there are three nitrogen-nitrogen bonds in N2, the overall bond order for the nitrogen atom in N2 is 3.
In summary, the bond order for the nitrogen atom in O2 is 1.5, while the bond order for the nitrogen atom in N2 is 3.