Untitled - Kelly Walsh High School

150 CHEMISTRY FOR THE UTTERLY CONFUSED
a bond angle of 120o . This type of bonding occurs in the formation of the Cto-C
double bond as in CH2=CH2. sp3 hybridization results from the mixing on one s-orbital and three porbitals,
resulting in four sp3 hybrid orbitals with a tetrahedral geometric orientation.
We find this sp3 hybridization in carbon when it forms four single
bonds with a bond angle of 109.5.
sp3d hybridization results from the blending of one s-orbital, three p-orbitals
and one d-orbital. The result is five sp3d orbitals with a trigonal bipyramidal
orientation., with bond angles of 90 and 120. This type of bonding occurs in
compounds like PCl5, an exception to the octet rule.
sp3d2 hybridization occurs when one s, three p, and two d-orbitals mix giving
an octahedral arrangement. SF6 is an example. Again, this is an exception to
the octet rule. If one starts with this structure and one of the bonding pairs
becomes a lone pair, a square pyramidal shape results; two lone pairs gives a
square planar shape. The bond angle is 90.
Figure 10-4 shows the hybridization that occurs in ethylene, H 2C=CH 2. Each
carbon has sp 2 hybridization. On each carbon, two of the hybrid orbitals overlap
with an s-orbital on a hydrogen atom to form a carbon-to-hydrogen covalent
bond. The third sp 2 hybrid orbital overlaps with the sp 2 hybrid on the other
carbon to form a carbon-to-carbon covalent bond. Note that each carbon has a
remaining p-orbital that has not undergone hybridization. These are also overlapping
above and below a line joining the carbons.
Figure 10-4 Hybridization in ethylene H 2C=CH 2
In ethylene, there are two types of bonds. Sigma (s) bonds have the overlap of
the orbitals on a line between the two atoms involved in the covalent bond. In
ethylene, the C-H bonds and one of the C-C bonds are sigma bonds. Pi (p)
bonds have the overlap of orbitals above and below a line through the two
nuclei of the atoms involved in the bond. A double bond is always composed of
one sigma and one pi bond. A carbon-to-carbon triple bond results from the