MO diagram of water : why does the 2s interact ?
http://www.ch.ic.ac.uk/vchemlib/course/mo_theory/
If you scroll down to the MO diagram of water you'll see that the 2s orbital on Oxygen is shown to interact with the a1 H2 orbital.
Surely the 2s O orbital is far too low in energy to do this.
The following is a picture from Group Theory for Chemists and shows exactly what I'm thinking. What's going on ?
The book explains that the two filled non bonding MOs are the two lone pairs we see on water.
If you scroll down to the MO diagram of water you'll see that the 2s orbital on Oxygen is shown to interact with the a1 H2 orbital.
Surely the 2s O orbital is far too low in energy to do this.
The following is a picture from Group Theory for Chemists and shows exactly what I'm thinking. What's going on ?
The book explains that the two filled non bonding MOs are the two lone pairs we see on water.
Original post by EierVonSatan
x
The reason I think the interaction is unlikely is in analogy to CO where the 2s on O is far too low in energy to interact with the 2s on C.
Original post by Ari Ben Canaan
x
The MO diagram you've linked to looks exaggerated. There can be some interaction because of the symmetry match, but you're right that it'll be (at best) very weak.
(edited 10 years ago)
Original post by BJack
The MO diagram you've linked to looks exaggerated. There can be some interaction because of the symmetry match, but you're right that it'll be (at best) very weak.
But it seems this interaction does show up reality albeit quite weakly as you have suggested. Its just really confusing tbh.
In an exam if I didnt show such an interaction for water I wouldnt go ahead with mixing any orbitals in the MO diagram and this would lead to lower marks.
I mean I get its qualitative and everything but its a bit too 'hand wavy' for me in instances.
Original post by Ari Ben Canaan
But it seems this interaction does show up reality albeit quite weakly as you have suggested. Its just really confusing tbh.
In an exam if I didnt show such an interaction for water I wouldnt go ahead with mixing any orbitals in the MO diagram and this would lead to lower marks.
I mean I get its qualitative and everything but its a bit too 'hand wavy' for me in instances.
In an exam if I didnt show such an interaction for water I wouldnt go ahead with mixing any orbitals in the MO diagram and this would lead to lower marks.
I mean I get its qualitative and everything but its a bit too 'hand wavy' for me in instances.
In an exam, you should explain the MO diagrams that you draw — "overlap from orbitals of same symmetry", "negligible overlap due to large energy difference can be ignored", etc.
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