H
H C H
methane, CH4
H
109.5°
less repulsion between the
bonding pairs of electrons
90°
H
..
H C H
H N H
H
H
ammonia
NH3
less repulsion between the bonding pairs of electrons
H
..
H C H
H N H
H
H
..
H O
.. H
water, H2O
109.5° (109.5°)
109.5° (107°)
109.5° (104.5°)
H
C H
H
H
N H
H
H
H
O
H
Ozone
O3
O
O
O
Formaldhyde
H2CO
H
C
H
O
Hydrogen
Cyanide
HCN
H
C
N
H
C
H
H
H
H
H
C
O
H
C
N
H
C
H
H
H
H
H
C
O
H
C
N
Are there atomic orbitals on C, Si, N and O to
accommodate the bonding electrons of the
shapes predicted by VSEPR?
3 p orbitals
s orbital
x
x
y
y
z
z
Are there atomic orbitals on C, Si, N and O to
accommodate the bonding electrons of the
shapes predicted by VSEPR?
x
x
y
y
z
z
Are there atomic orbitals on C, Si, N and O to
accommodate the bonding electrons of the
shapes predicted by VSEPR?
4 sp3 orbitals
x
y
z
Are there atomic orbitals on C, Si, N and O to
H
accommodate the bonding electrons
of the
shapes predicted by VSEPR?
4 sp3 orbitals
C
x
H
y
z
H
H
s + px + py = 3 sp2 orbitals
H
H
C
O
pz orbital
H
H
C
O
H
H
H
C
O
C
H
O
H
H
C
O
H
H
C
O
s + px = 2 sp orbitals
H
Py orbital
Pz orbital
C
N
H
C
N
C
N
H
C
N
C
N
H
C
N
C
N
H
C
N
C
N
H
H
C
N
C
N
bonding
hybrid
orbitals
VSEPR
shape
tetrahedral
sp3
trigonal
planar
sp2
linear
sp
Review: Ethane
3
sp
Csp3-Hs
Csp3-Csp3
Review: Ethane
Csp3-Hs
3
sp
H
H
C
●
●
C
H
H
H
Csp3-Csp3
H
Hybrid atomic orbitals
+
s orbital
and
p orbital
x
s+ p
x
Why are hybrid orbitals used in chemical bonding?
..
. .
s- p
x
molecular orbitals. a C-C bond
Csp3
energy
Csp3
molecular orbitals. a C-C bond
Csp3
energy
Csp3
molecular orbitals.
a C=C bond
Csp2
energy
Csp2
A model of ethene using hybrid
and atomic orbitals.
·
··
·
H
C
H
σ-bond
H
C
H
H
H
C C
H
H
π-bond
molecular orbitals.
a C=O bond
H
C O
H
In contrast to the rotation about single bonds, the
rotation about double bonds is very difficult.
C
12 kJ
energy
z
y
x
2s
2px
2pz
2py
Important consequences of
Quantum Mechanics
The locations of the electrons are described
by atomic orbitals.
A given orbital can contain only 2 electrons.
(Pauli exclusion principle.)
Each orbital has an associated energy and electrons will
occupy the lowest energy orbitals first.
Atomic orbitals on different atoms will can combine to
give molecular orbitals, but only if their symmetry matches.
good s bond
bad – wrong symmetry
No bonding!
These atomic orbitals and their hybrids will be used
extensively in our models of chemical bonding.
p orbitals
s orbital
x
H
y
z
C, N, O
Common hybrid orbitals used in bonding of
carbon, nitrogen and oxygen.
sp
x
y
z
2s
2px 2py 2pz
Common hybrid orbitals used in bonding of
carbon, nitrogen and oxygen.
sp
hybrid orbital angle 180°
pz
sp
sp
py
2s
2px 2py 2pz
Common hybrid orbitals used in bonding of
carbon, nitrogen and oxygen.
2
sp
hybrid orbital angle 120°
pz
2s
2px 2py 2pz
Common hybrid orbitals used in bonding of
carbon, nitrogen and oxygen.
3
sp
2s
hybrid orbital angle 109.5°
2px 2py 2pz
Methane
3
sp
Csp3-Hs
H
H
C
H
H
Ethane
3
sp
H
C
H
H
H
Ethane
3
sp
H
H
C
●
●
C
H
H
H
H
Ethane
Csp3-Hs
3
sp
H
H
C
●
●
C
H
H
H
Csp3-Csp3
H
Ethane
3
sp
Csp3-Hs
Csp3-Csp3