Since the hybridization of the central atom is usually the only factor needed to determine molecular shape, you can simplify by considering only the hybridization of the central atom. Using this simplified method, the O atom of CO2 would bond with one of its p or s orbitals. Use valence bond theory to devise a hybridization and bonding scheme for CO2.

CO2 contains sp hybridized carbon and sp2 oxygen atoms (linear shape)

Explanation:

There are two sigma bonds and two pi binds in the CO2 molecule. Carbon in its ground state contains one outer 2s orbital filled with two electrons and two outer 2p orbitals which are singly filled. Oxygen contains in its ground state contains an outer 2s orbital and three 2p orbitals filled with four electrons.

When these orbitals on oxygen are sp2 hybridized, one orbital is left unhybridized in each oxygen atom. Recall that two hybrized sp2 orbitals on oxygen atom accommodate the two lone pairs and one sp2 hybridized orbital in each oxygen atom forms a sigma bond to carbon. The remaining unhybridized orbital on oxygen is used by each oxygen atom to overlap with each unhybridized p orbital on the sp hybridized carbon.

Carbon forms two sigma bonds to oxygen via the two hybridized sp orbitals on carbon. The two unhybridized orbitals overlap sideways and firm pi bonds with oxygen p orbitals.

Triatomic molecules must be either linear or bent. In CO2, the bond angle must be 180° giving a linear molecule.