CHM 401

 

Molecular Orbital Theory

Experimentally, O2 is found to have two unpaired spins – VBT can not explain a simple molecule like O2 !

 

Linear Combination of Atomic Orbitals

Assumptions:

1) Molecular Orbitals look like atomic orbitals, especially near the nucleus

2) Molecular Orbitals are constructed by interference patterns of atomic orbitals

3) The total number of molecular orbitals = the total number of atomic orbitals

4) Molecular wavefunctions are products of the molecular orbital functions

 

Overlap of atomic orbitals

constructive interference gives bonding orbital, no nodes

destructive interference gives antibonding orbital one node, perpendicular to the internuclear axis

 

 

 

 

 

 

molecular orbitals are labeled by nodal properties:

0 nodes parallel to the internuclear axis: σ

1 node parallel to the internuclear axis: π

2 nodes parallel to the internuclear axis: δ

0 nodes perpendicular to the internuclear axis: bonding

1 node perpendicular to the internuclear axis: antibonding