- required to solve contradiction of observed degenerate bonds of methane
- imagine as a redistribution of energies
the three atomic orbitals formed by the s-p interaction are degenerate, but the energy of the s-s interaction is different
- has three-quarters of p orbital character
- has one-quarter character from s orbital
- planar node through nucleus
- one lobe is larger
- energy of sp3 orbitals are average of 2 2s electrons and 2 2p electrons (degenerate)
- energy to promote one 2s electron to 2p is called promotion energy
- offset by bond formation energy
- any atomic orbital can be hybridised
- it is preferable to have a very high energy antibonding MO that is unfilled as opposed to an empty orbital that is lower in energy
i.e. lowest energy orbitals should be populated
