Hybrid orbitals can
- overlap with hybrid orbitals or s orbitals on adjacent atoms to give σ(single) bonds.
- accomodate nonbonding electron pairs
Therefore the number of hybrid orbitals required at a particular atom depends on the number of σ bonds at that atom and the number of nonbonding electron pairs.
The appropriate hybrid set to describe the bonding at an atom is chosen by
- drawing the Lewis structure of the species containing the atom
- counting the number of nonbonding electron pairs at the atom and add to this the number of σ bonds formed by that atom. This number equals the number of hybrid orbitals required to describe the bonding at that atom.
- choosing the hybrid set which contains that number of orbitals