Electron Promotion:
When an electron from a lower shell like an “s” orbital goes up into a “p” orbital.
It is VERY easy for carbon because the required promotion energy is low
It is ONLY elements with empty “p” orbitals that can do this, so NO oxygen or F, but Boron can.
However, they still hybridize, but promotion just can’t happen.

Hybrid Orbitals AKA sp3 hybrids:
Each h-orbital is the amplitudes of the orbitals added, but the orientation changes because of the “-” sign.

Hybridization:
When the hybrid orbitals are created it means that they ALL have equal energy.

Hybridization of not methane:
Follow the VESPR model, so for ethane, it is just two tetrahedral’s/methane’s bonded over sigma
AND
Ammonia (NH3) is also tetrahedral, which means it can be looked at as 4 sigma bonds in the form of sp3.

Period 3+ d orbital hybrids:
For elements with “d” orbitals, they also have hybridization labeled as sp3d, sp3d2, etc.
However, you’ll never get to “d” orbital stuff.