Hybridization | DAT
Review: Atomic Orbitals
• The electrons of an atom will fill
atomic orbitals in a specific order
• For carbon, with 6 electrons:
Atomic Orbital Configuration for Carbon
•
We know that only valence
electrons bond, so let’s look only
at the 4 electrons in the 2nd shell
Formation of Hybrid Orbitals
• If carbon forms 4 sigma bonds
with hydrogen, each of its 4
valence electrons is participating
in a bond
Formation of Hybrid Orbitals
The electrons from the s and p subshells move
into hybrid orbitals at an energy between the two
subshells. Now, all the valence electrons are
equal in energy.
Naming Hybrid Orbitals
• To name, hybrid orbitals, count
the number of sigma bonds and
lone pairs on an atom
• Then, using the template s#p#,
assign the count to each letter
o S’s # cannot exceed 1
o P’s # cannot exceed 3
• So, for instance, suppose we
wanted to know the hybridization
of the leftmost nitrogen in N2O:
Molecule of N2O
•
Carbon Forms 4 Sigma Bonds with Hydrogen
•
•
Since each bond is identical, the
electrons in each bond should be
identical in energy
o But this contradicts our
atomic orbital diagram
o In the diagram, we said
the 2s electrons were
lower in energy than the
2p electrons
To resolve this, hybrid orbitals
form when bonds form
o Energy of hybrid orbitals
will be between that of
the s and p subshells
•
•
•
•
•
The leftmost nitrogen has 1 lone
pair 1 sigma bond
o Recall that even double
and triple bonds only
have 1 sigma bond
So the total count is 2
Assign the 2 to the s#p# template:
o s1 p 1
o Superscript 1s are
generally hidden, making
it sp
Let’s also do the oxygen; it has:
o 1 sigma bond
o 3 lone pairs
So the count is 4, making its
hybridization s1p3, which reduces
down to sp3
The middle nitrogen will have sp
hybridization
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Hybridization | DAT
•
If our sum exceeded 4, we’d
have to introduce a d to the front
of the hybridization, as in dsp3
and d2sp3
o Though we write the d in
the front, it is introduced
last- only when needed
Character of a Subshell in a Hybrid
Orbital
• When a hybrid orbital forms, it
forms between two different
subshells
o We can find out how
much the hybrid orbital is
“influenced” by each of
the starting subshells
o This is known as the
subshell’s “character”
• This is done using the
superscripts:
o A hybridization of sp3 is
1 part s and 3 parts p
• S-character is ¼,
or 25%
• P-character is ¾,
or 75%
o An sp hybridization is 1
part s and 1 part p:
• S-character and pcharacter are both
50%
• A hybrid orbital with greater scharacter will be closer in energy
to the s-subshell energy level
Energy of sp3 Hybrid Orbitals
Since sp3 hybrid orbitals have greater pcharacter, they will be closer in energy to the
initial p-subshell.
•
A lower energy for the hybrid
orbitals indicates stronger
bonding
o So, sp bonding (i.e. triple
bonds) are stronger than
sp3 bonds (single bonds)
VSEPR Theory
• Knowing molecule
hybridizations, it is possible to
predict the geometric shapes
formed by molecules
• On the next page, we
demonstrate how bond angles
and shapes can be predicted,
given hybridization and the
number of lone pairs on an atom
• It is useful to know the various
shapes
o Rather than try and
strictly memorize each
shape, perhaps try to see
how electrons and bonds
are repelling one another
to form the lowest energy
configuration
Energy of sp Hybrid Orbitals
The sp hybrid orbitals are 50% s and 50% p in
character. So, their energy will be at a midpoint
between the s and p energies.
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Hybridization | DAT
VSEPR Theory Shapes
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© 2017 J Co Review, Inc., Accessed by Guest on 07-31-2017