Refer to Section 5.3 Hybrid Atomic Orbitals (1).

The hybridization of the centre atom will be determined by the electron-pair geometry, not the atom itself. For example, the centre atoms hybridization will always be sp in a linear molecule.

Number of electron domains (as determined by the number of bonding directions and lone pairs in the best Lewis structure) = Number of atomic orbitals required for hybridization.

Number of hybrid orbitals = Number of orbitals mixed.

Hybrid orbitals are named by type and number of orbitals mixed.

Recall the atomic orbitals: for n=2 there is 1 ‘s’ orbital (l=0) and 3 degenerate ‘p’ orbitals (l=1).

Note that ‘d’ orbitals (l=2) can only exist when n is greater than or equal to 3.

• 2 domains = 2 atomic orbitals must be hybridized = s + p = sp hybridization = linear electron domain geometry (EDG)
• 3 domains = 3 atomic orbitals must be hybridized = s + p + p = sp² hybridization = trigonal planar EDG
• 4 domains = 4 atomic orbitals must be hybridized = s + p + p + p = sp³ hybridization = tetrahedral EDG
• 5 domains = 5 atomic orbitals must be hybridized = s + p + p + p + d = sp³d hybridization = trigonal bipyramidal EDG
• 6 domains = 6 atomic orbitals must be hybridized = s + p + p + p + d + d = sp³d² hybridization = octahedral EDG