Can you please explain the shape of the CO2 molecule on the basis of Valence Bond theory?
The electronic configuration of carbon in the ground state is 1s22s22px12py12pz . In the formation of carbon dioxide molecules the 2s orbital and the vacant p orbital hybridise together to form two equivalent sp orbitals. These two sp orbitals have same energy and same shape. Thus in sp hybridised oxygen atom, we have two sp orbitals and two pure p-orbitals.
Oxygen on the other hand has two singly occupied p-orbitals. Its electronic configuration is 1s22s22px22py1 2pz1. Therefore the sp orbitals of carbon overlap with a p orbital of each oxygen atom along the internuclear axis resulting in the formation of two sigma bonds. We are now left with 2 unhybridised pure p orbitals of carbon and two unhybridised orbitals pure p of carbon. All of these are singly occupied. The p orbital of carbon overlaps with the p-orbital of oxygen sideways, resulting in the formation of pi-bond. Thus we have two pi bonds.
Therefore in oxygen atom , there are two sigma bonds and two pi bonds. The hybridisation is sp.