CHM 401

 

Construction of Energy Level diagrams

1) Define the basis set (i.e., the set of atomic orbitals to be used, generally the valence orbitals)

2) # of MOs = # of AOs

3) The change in energy is proportional to the degree of overlap

4) Better overlap occurs between AOs of about the same energy

5) Bonding orbitals lower energy, antibonding orbitals raise energy relative to the AOs

 

Bond Order = BO = ½(# electrons in bonding orbitals - # electrons in antibonding orbitals)

 

H2

BO = 1, same as VBT

 

First row diatomics basis set : 2s and 2p (1s is a core orbital, so will not be affected much by bonding)

A2

configuration

B.O.

predicted spins

observed spins

Li2

2

1

0

0

Be2

21σ*2

0

0

0

B2

21σ*22

1

2

2

C2

21σ*24

2

0

0

N2

21σ*224

3

0

0

O2

21σ*2241π*2

2

2

2

F2

21σ*2241π*4

1

0

0

Ne2

21σ*2241π*42σ*2

0

0

0