hybrid orbitals [ENDORSED]

[Tylina Guo 1K]

why are some orbitals hybridized and some not, like in C (3 are hybridized and 1 is not)?

[Ethan Cheng 2k]

It depends on which C you're looking at. If the C has four regions of electron density around it, it would have four sp3 hybrid orbitals and zero unhybridized orbitals. If the C has only three regions of electron density around it (2 single bonds and 1 double bond), it would only have three sp2 hybrid orbitals that each holds one electron; the remaining electron would be in an unhybridized p orbital and forms a double bond with another electron in an unhybridized p orbital of another atom.