Molecular Orbitals of HF

The H atom is slightly nearer the viewer than the F atom.

Different types of approximate calculation yield fundamentally similar shapes, especially with respect to arrangement of nodes.
For the qualitative purposes of Chem 125 we are intersted in these similarities rather that in the differences of detail.
A dramatic difference is in the sophistication of the graphical presentation, in some ways the older, simpler presentation may be clearer.
Improved MOs calculated today
in less than 1 minute on a laptop

contoured where e-density would be 0.001 e/Å3
relatively far from nuclei
(note scale of bond lengths)
Crude MOs calculated 25 years ago,
when it was a real accomplishment
using room-filling computers

contoured where e-density would be 0.07 e/Å3
much higher value of psi; closer to nuclei
LUMO (σ*)

antibonding
left-overs
mostly H1s
with F2p

 

 

 
Degenerate
HOMOs
(np)

F2p AOs
with no H1s
(why?)

(σ,n)

Mostly F2p
distorted
by bonding
with a little H1s
Lowest valence-
level MO (σ,n)

Mostly F2s
distorted
by bonding
with a little H1s

From MacSpartan Plus [3-21G(*) AOs]
From Salem and Jorgensen, Organic Chemist's Book of Orbitals
Academic Press, 1973

Return to Examples of MOs
Return to Chem 125 Homepage