Forgive me for such a such a question; it's probably sleep deprivation or my inherent stupidity. Either way, where do vacant p-orbitals come from?? When carbon's valence electrons find themselves in a bonding situation that requires them to hybridize, their 2s and 2p orbitals merge into a single ##sp^3## orbital. Apparently the "3" refers to the number of 2p orbitals that merged, but I don't understand why there are three?? There are only two unpaired electrons from 2p.