The hybridization of sulfur dioxide (SO2) is sp2. This is determined by examining the molecular geometry and electron pair arrangement around the sulfur atom.
In SO2, the sulfur atom is surrounded by two oxygen atoms and has one lone pair of electrons. To accommodate these three regions of electron density, the sulfur atom undergoes hybridization to form three sp2 hybrid orbitals. Two of these orbitals form sigma bonds with the oxygen atoms, while the third contains the lone pair of electrons.
The resulting electron geometry is trigonal planar, and the molecular geometry is bent due to the presence of the lone pair, which repels the bonding pairs. This hybridization and arrangement explain the bond angles in SO2, which are approximately 120 degrees.