http://www.ck12.org Chapter 9. Covalent Bonding
FIGURE 9.42
The expanded octet trigonal bipyramidal
and octahedral geometries are a result
ofsp^3 dandsp^3 d^2 hybridization, respec-
tively.Hybridization in Molecules with Double or Triple Bonds
The hybridization model helps explain molecules with double or triple bonds. Consider the ethene molecule (C 2 H 4 ).
In the lesson, “Lewis Electron Dot Structures,” we saw that C 2 H 4 contains a double covalent bond between the two
carbon atoms and single bonds between the carbon atoms and the hydrogen atoms. The entire molecule is planar.
FIGURE 9.43
As can be seen above (Figure9.43), the electron domain geometry around each carbon atom is trigonal planar,
which corresponds tosp^2 hybridization. Previously, we saw carbon undergosp^3 hybridization in a CH 4 molecule,
so how does it work in this case? As seen below, the electron promotion is the same, but the hybridization occurs
only between the singlesorbital and two of the threeporbitals. Thus generates a set of threesp^2 hybrids along with
an unhybridized 2pzorbital. Each orbital contains one electron and is capable of forming a covalent bond.