Hybridization
In this process an atom adopts a different set of bonding orbitals compared to ground
state orbitals. For example, an atom might combine one s and two p orbitals to give three new
hybrid orbitals each having characteristics of both s and p orbitals (hence the term hybrid). What
is the purpose of hybridization? Twofold:


to maximize half-filled orbitals
hybrid orbitals are net lower in energy
To determine the hybridization of an atom in a molecule, count the number of effective
pairs around that atom. Lone pairs (nonbonding pairs), single bonds, double bonds,
and triple bonds all count as one effective pair.
1s22s22p2
Consider C:
2p
___ ___ ___
___ ___ ___
___ ___ ___ ___
E
2s
___
___
e- promotion
ground state
(two half-filled)
hybridization
excited state
four sp3 hybrid orbitals
(four half-filled)
Whenever an atom is surrounded by four effective pairs, a set of sp3 hybrid orbitals is required.
How do three orbitals arrange themselves farthest apart around a central atom to minimize
repulsions?