sp3 Hybridization: a scheme for tetrahedral
and related species
The notation sp3 means that one s and three p atomic orbitals
mix to form a set of four hybrid orbitals with different
directional properties.
A similar scheme to those described above can be derived to
generate four sp3 hybrid orbitals from one 2s and three 2p
atomic orbitals. The sp3 hybrid orbitals are described by
the normalized wavefunctions in equations 4.6–4.9 and are
shown pictorially in Figure 4.6a. Each sp3 hybrid orbital
possesses 25% s character and 75% p character, and
the set of four equivalent orbitals defines a tetrahedral
framework.
sp3 hybrid ¼ 1
2 ð 2s þ 2px þ 2py þ 2pz
Þ ð4:6Þ
sp3 hybrid ¼ 1
2 ð 2s þ 2px 2py 2pz
Þ ð4:7Þ
sp3 hybrid ¼ 1
2 ð 2s 2px þ 2py 2pz
Þ ð4:8Þ
sp3 hybrid ¼ 1
2 ð 2s 2px 2py þ 2pz
Þ ð4:9Þ
In Figure 4.6b we illustrate how the tetrahedral structure of
CH4 relates to a cubic framework. This relationship is
important because it allows us to describe a tetrahedron in
terms of a Cartesian axis set. Within valence bond theory,
the bonding in CH4 can conveniently be described in terms
of an sp3 valence state for C, i.e. four degenerate orbitals,
each containing one electron. Each hybrid orbital overlaps
with the 1s atomic orbital of one H atom to generate one
of four equivalent, localized 2c-2e CH -interactions.
Worked example 4.1 Hybridization scheme for the
nitrogen atom in NH3
Use VSEPR theory to account for the structure of NH3,
and suggest an appropriate hybridization scheme for the N
atom.
The g