Hybridization
sp3 Hybridization efficently bonds to four atoms and lone pairs
Mix 3 carbon p + 1 carbon s to get 4 equivalent sp3 orbitals (sp3 = 1 part s, 3 parts p)
H
y
H
4 sp3 orbitals
H
C
+
z
x+
+
H
2s1
2py1
2px1
2pz1
note: an excited state configuration
We now have 4 sp3(C)-s(H) bonds of equal length at 109.5° apart.
Hybridization with multiple bonds
H
H
C
We need 3 orbitals to make 3 bonds
C
H
Mix 2 carbon p + 1 carbon s to get 3 equivalent sp2 orbitals
H
C
+
z
2s1
2px1
y
The remaining
orbital is an
unhybridized p
orbital
H
H
3 sp2 orbitals
x+
H
C
sp2 σ
2pz1
120° C
Each unpaired electron on
carbon forms a bond with the
other unpaired electron (this
forms a π bond)
π
H
H
H
H
2py1
H
C
C
This time, we only need 2 orbitals to make 2 bonds:
Mix 1 carbon s, 1 carbon p to get 2 equivalent sp orbitals
x
+
C
2s1
H
sp σ
sp
2px1
180° C
π
π
y
H
The remaining
orbitals are
unhybridized p
orbitals
z
2pz1
2py1
C
C
C
C
Each unpaired electron on carbon forms a bond with
the other unpaired electron (this forms a π bond)
Note that these orbitals (px and pz) are 90°C apart.
H
Example Problems
H
H
Guide for determining hybridization:
1. Draw a good Lewis structure.
2. Focus on an atom and sum up:
# bonded atoms + # of lone pairs
C
C
H
O
H
O
3 bonded atoms +
0 lone pairs
Sum of 3 means sp2 hybridization, 120°C
3. This will give a sum between 2-4:
Sum
2
3
4
3 bonded atoms + 1 lone pair
Hybridization Geometry Bond angle
sp
linear
180°
sp2
trigonal planar 120°
sp3
tetrahedral 109.5°
H
H
Note: This is a guide not an absolute rule.
Atoms will rehybridize to place lone pairs in conjugated
p-orbitals if that can lower energy
3rd row elements can access d-orbitals.
C
O
H
H
H
H
C
3 bonded atoms + 0 lone pairs
sp2
N
H
H
H
C
Sum of 4 means
sp3 hybridization
109.5°C
hybridization, 120°C
H
C
C
C
C
H
N
3 bonded atoms + 0 lone pairs
sp2 hybridization, 120°C
H
2 bonded atoms + 1 lone pair
2 bonded atoms + 2 lone pairs (not shown, but
sp2
hybridization
120°C
can be determined from a good Lewis Dot structure)
sp3 hybridization, ~109.5°C
(lone pair not shown, but can be
determined from a good Lewis Dot
structure)
HO
N
O
C
H3C
R
CH3
C
H
C
N
N
sp hybridization,
180°C
2 bonded atoms
+ 1 lone pair (*see note above)
sp2 hybridization, 120°C
NH2
B
A
E
Challenge Problem!
Identify the hybridization
and bond angle of each
atom indicated.
2 bonded atoms + 0 lone
pairs
O
O
P
O
O
O
N
O
P
O P
O
O
N
O
CH2
H
O
H
H
OH
H
C
N
C
N
H
D
H
A) sp3 , 109.5°C B) Appears to be sp ,
but sp2 due to resonance
3
C) sp2, 120°C D) sp2 ,120°C E)sp d, 109.5°
3