Hybridization scheme for linear triatomic molecules

If we prefer to describe the bonding of a polyatomic molecule using localized two-center, two-electron (2c-2e) bonds, we can turn to the hybridization theory, which is an integral part of the valence bond method. In this model, for AX systems, we linearly combine the atomic orbitals on atom A in such a way that the resultant combinations (called hybrid orbitals) point toward the X atoms. For our BeH2 molecule in hand, two equivalent, colinear hybrid orbitals are constructed from the 2s and 2pz orbitals on Be, which can overlap with the two Is hydrogen orbitals to form two Be-H single bonds. (The 2p and 2py 

So now we have two equivalent bonding orbitals Vt and if2 with the same energy. Moreover, and 1 2 are localized orbitals ir is localized between Be and Ha and 2 between Be and H. They are 2c-2e bonds. 

Carbon dioxide is a linear molecule with both a and jt bonds. The coordinate system chosen for CO2 is shown in Fig. 3.4.4. Once again, the molecular axis is taken to be the z axis. The atomic orbitals taking part in the bonding of this molecule are the 2s and 2p orbitals on C and the 2p orbitals on O. There are a total of ten atomic orbitals and they will form ten molecular orbitals. 

The a orbitals in CO2 are very similar to those in BeH2. The only difference is that the oxygens make use of their 2pz orbitals instead of the Is orbitals used 

The it molecular orbitals are made up of the 2px and 2p-y orbitals of the three atoms. Let s take the 2p orbitals first. The two 2px orbitals can be combined in two ways  

---