Why VSEPR Theory is not completely theoretically proven?

[Tiny_Explorer]

Why fundamental level of VSEPR Theory is more far away from understanding ?

 

[berkeman]

Can you post links to the reading you have been doing to try to answer your question? Thanks.

 

[Tiny_Explorer]

Can you post links to the reading you have been doing to try to answer your question? Thanks.

It is from the NCERT Chemistry Textbook , it says " The VSEPR Theory is able to predict geometry of a large number of molecules, especially the compounds of p-block elements accurately. It is also quite successful in determining the geometry quite-accurately even when the energy difference between possible structures is very small. The theoretical basis of the VSEPR theory regarding the effects of electron pair repulsions on molecular shapes is not clear and continues to be a subject of doubt and discussion."

 

[Mayhem]

Weird phrasing for a textbook. There is no good way to answer your question. Do you have example of where VSEPR fails (there are many) that you would like input on?

 

[Borek]

Disclaimer: QM is something I licked 40 years ago as part of the curriculum, it was way too bitter for my taste, so I don't pretend to "know".

My take is that the problem is in what we understand as an "electron pair". Is it a well defined quantum object? Not so much, well defined object with electrons is an orbital and there is no orbital occupied by the "electron pair". Do we see an area with the increased electron density were we expect "electron pair" to reside? Yes, definitely, once we calculate electron density such areas exist. So the opinion on VSEPR depends on how rigorous your approach to QM is.

Yes, it is useful, yes, it is handwavy.