Before I start of this question, Ι want to make it clear that I know that hybridization, like pretty much all of chemical bonding, are just made up to qualitatively rationalize observations. I know that theres no actual orbital overlapping, resonance, excitation.... and what not, and the only real things governing "bonding" are electrodynamics and quantum mechanics
When I first came across hybridization, I learnt that it is just used to obtain the correct electron density distribution from atomic orbitals as the experimentally observe corresponding to least repulsion/energy. The go-to way to determine hybridization would then be to use VSEPR to find the most stable electron domain geometry. However, I've come across several molecules such as H2S, PH3 and Halogen molecules where there is no hybridization. How does VBT /hybridization theory rationalize this? And is there any way that I could predict it? (I obviously can't know the experimental observations for all possible molecules before hand)
Secondly, is rationalizing geometry the only reason for invoking hybridization? I have come across these 2 other reasons in several reliable textbooks:
- Hybridization occurs as hybrid orbitals are able to overlap more effectively and the bond strength is proportional to the extent of overlap. While this seems somewhat logical, I can't think of a single molecule where better overlap needs to be the reason for a specific hybridization
- Hybridization occurs inorder to make all orbitals degenerate before overlapping as this corresponds to the lowest energy "quantum mechanically". This one seems way too handwavy but is mentioned on wikipedia https://en.wikipedia.org/wiki/Orbital_hybridisation
Bonus question: I have another small question that I dont want to start another thread about given the multitude of questions on hybridization already present on the site but feel free to ignore this.
Why exactly do sp,sp2 & sp3 hybrid orbitals have the same exact geometries as the ones observed in electron domains? Is it just a coincidence or are they forcefully combined in such a way to match them>