Why doesn't an sp3s hybridisation exist? Trying to prove that nitrogen doesn't split its lone pair to form 5 bonds, I thought of a situation that I couldn't rule out; the paired electron being excited to the 3s orbital, so that five bonds could be formed- in an &quot;$\ce{sp3s}$&quot; hybridisation.
I know hybridisation is just an observation-based explanation, but I'd like to know how to rule wacky situations like this out.
Can this - and all other nonstandard hybridisations you can come up with - be ruled out by reasoning that the electron excitations involved take up too  much energy?
The counter question that might help you rule this out is: &quot;Which 3s orbital?&quot; Note that atomic Nitrogen doesn't have a 3s orbital as N itself belongs to the 2nd period(n=2).

Also note that in hybridization, Atomic orbitals of same or almost similar energies intermix to form same number of new Hybrid orbitals of same shap and equivalent energy.
That being said, you cant expect 2s or 2p orbitals to intermix with a 3s orbital
(if it was a case. Since this case isn't possible with N)