1
Resonance is One Way to Describe
Delocalized Bonding
Molecular Orbital Theory (MO) is another
way to describe Delocalized Bonding
H atom
HH molecule
Section 6.5
MO Theory
The orbitals of a molecule result from the addition
or subtraction of valence atomic orbitals
Since es travel in waves, the addition or subtraction
of atomic orbitals can be constructive or destructive
+
+
Section 6.5
Molecular Orbital Theory (MO)
+
Red
:
represents the
wave function when
algebraic sign is positive

Blue
:
represents the
wave function when
algebraic sign is negative
nucleus
atomic orbital
AO
molecular orbital
MO
Section 6.5
MO Theory
– Bonding MO’s
+
=
bond
Bonding MO
s orbitals
p orbitals
+
=
bond
Bonding MO
Section 6.5
p orbitals
+
=
bond
Bonding MO
constructive
MO Theory
– Antibonding MO’s
Section 6.5
+
=
bond
Antibonding MO
s orbitals
Nodal plane
–
region of no
e density
+
=
p orbitals
bond
Antibonding MO
+
=
p orbitals
bond
AntiBonding MO
destructive
AO
1
s
E
orbital
Bonding MO
Antibonding MO
orbital
Nodal plane
–
region of no
e density
# MO = # AO
Bonding in H
2
AO
1
s
+
+
Section 6.5
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