Other Hybrid Orbitals
Hybrid orbitals can be formed by mixing more than just two simple atomic orbitals. If an s and two p orbitals combine, three hybrid orbitals, each similar in shape to the sp hybrids, are formed. they are called sp2 hybrid orbitals, the superscript 2 specifying the number of p orbitals taking part in the formation of the hybrids. Also, notice that the number of hybrids is the set is equal to the number of simple atomic orbitals from which the hybrids are formed.
 

 
BCl3 is a molecule in which the central boron atom uses sp2 hybrids for bonding. A boron atom has the valence shell configuration
 

 
To form three bonds, boron must have three half-filled orbitals, so its 2s electrons must become unpaired. The resulting half-filled s and p orbitals then become hybridized.
 
A chlorine atom has the valence shell configuration 1s2 2s2 2p5 , the half-filed 3pz orbital of each chlorine overlaps with one of the sp2 hybrids of boron to give the molecule.
 
These bonds are illustrated below. The geometry of the BCl3 molecules is planar triangular because all three hybrid orbitals fit nicely into the plane of the equator, 120o apart.
 

 
The list below shows important types of hybrid orbitals. The directional properties of the various hybrids are also shown.
 
sp  hybrids 
sp2 hybrids 
sp3 hybrids 
sp3d hybrids 
sp3d2 hybrids 
 
The bonds in the ethane molecule. Notice the overlap in the orbitals. The degree of overlap of the sp3 orbitals in the carbon-carbon bond does not appreciably affect the rotation of the two CH3- groups.