Question
Using the orbital overlap concept, explain the formation of:
(i) O2 molecule (ii) N2 molecule.
Solution
(i) O2 molecule: The electronic configuration of oxygen atom
(z = 8) is
It has two half filled 2p-orbitals in its valence shell. In the formation of the oxygen molecule. One of the two half filled 2p-orbitals of each oxygen atom overlaps mutually along the internuclear axis to form σ bond. The other half-filled 2p orbitals of each oxygen atom undergo sidewise overlapping to form
-bond.
Thus, two oxygen atoms are linked together by a double bond, one of which is sigma bond and other is
a bond.
(ii) N2 molecule. The electronic configuration of nitrogen atom (Z = 7) is
It has three half filled 2p-orbitals in its valence shell. In the formation of the nitrogen molecule, one of the three half-filled 2p orbitals of each nitrogen atom overlaps mutually along the internuclear axis to form a bond. The other two 2p-half filled orbitals of a nitrogen atom undergo sidewise overlapping with their parallel oriented 2p-orbitals of other nitrogen to form two 
bonds. Thus, two nitrogen atoms are linked together by a triple bond, one of which is sigma bond and the other two are 
bonds.
(z = 8) is
It has two half filled 2p-orbitals in its valence shell. In the formation of the oxygen molecule. One of the two half filled 2p-orbitals of each oxygen atom overlaps mutually along the internuclear axis to form σ bond. The other half-filled 2p orbitals of each oxygen atom undergo sidewise overlapping to form
-bond.Thus, two oxygen atoms are linked together by a double bond, one of which is sigma bond and other is
a bond. (ii) N2 molecule. The electronic configuration of nitrogen atom (Z = 7) is
It has three half filled 2p-orbitals in its valence shell. In the formation of the nitrogen molecule, one of the three half-filled 2p orbitals of each nitrogen atom overlaps mutually along the internuclear axis to form a bond. The other two 2p-half filled orbitals of a nitrogen atom undergo sidewise overlapping with their parallel oriented 2p-orbitals of other nitrogen to form two bonds. Thus, two nitrogen atoms are linked together by a triple bond, one of which is sigma bond and the other two are bonds.
