[person123]

I am having trouble with question that ask for the hybridization of specific carbon and oxygen atoms in a molecule.
If oxygen has 6 valence electrons (enough to fill one s orbital and two p orbitals) then why does it not always have sp2 hybridization?
Likewise, why does carbon not always have sp hybridization?

[Yggdrasil]

Hybridization occurs when atoms bond to each other.  The shared electrons between atoms in a chemical bond help fill some of the empty orbitals in the atoms.  For example, when carbon bonds with four hydrogens in methane, each hydrogen shares an electron with carbon, so carbon will have eight electons in its outer shell in methane.

Plus, even though the oxygen atom has 6 electrons, there will be two in the s orbital and one p orbital will have two electrons and the other two p orbitals will have one electron each.  Having one full s orbital, two full p orbitals, and one empty p orbital would violate Hund's rule.