Beyond Lewis symbols for atoms: Hybrid Orbitals and π systems

Only molecular fragments are shown here, for the sake of clarity

Orbital hybridization is a model which consists in mixing atomic orbitals into new hybrid orbitals suitable for the pairing of electrons to form chemical bonds. It is closely related to Lewis structure and it is an integral part of organic chemistry. Although still used in several documents to describe the electronic structure and the bonding of transition metal complexes or hypervalent molecules, hybridization theory, when applied to these systems, is inadequate in most cases.

In other words, the range of validity of the hybrid orbitals model barely goes beyond organic chemistry. The molecular orbitals model should be preferred for a more approriate understanding of the electronic and structural properties of inorganic compounds.