Answer to Question #59813 in General Chemistry for Mark Adams

Question

One of the canonical structures for sulfur dioxide - SO2 - has sulfur double bonded to each oxygen atom to form a total of 4 bonds for sulfur - which can be achieved via valence expansion into empty d-orbitals.

What then is the hybridization of the valence-expanded sulfur?
It is described as SP2. But how can that be? This seems unlikely
because d-orbitals are involved since sulfur underwent valence
expansion.

On might imagine a pair of electrons from the 3S/3P oribital(s) being promoted to an empty d-orbital and then having the 3S and 3P orbitals hybridize in to SP2.
If this is true it would mean that the lone electron pair of the
valence-expanded sulfur consists of 2 electrons occupying
and unhybridized d-orbital. But is this correct??