In sulfuric acid (H₂SO₄), sulfur is indeed sp³ hybridized when it forms four sigma bonds. The reason for this lies in the electronic structure and the valence electron configuration of sulfur.
Sulfur, as an atom, has six valence electrons (2s²2p⁴). To form four sigma bonds in sulfuric acid, sulfur needs to have four orbitals available for bonding. Hybridization is a concept that allows atoms to rearrange their orbitals to form new hybrid orbitals suitable for bonding.
In the case of sulfur, one of the 3p orbitals and all three of the 3d orbitals can participate in hybridization to form four sp³ hybrid orbitals. By mixing one 3s orbital and three 3p orbitals, sulfur can generate four equivalent sp³ hybrid orbitals. These hybrid orbitals have a tetrahedral arrangement around the sulfur atom, which allows for the formation of four sigma bonds with the oxygen atoms in sulfuric acid.
It's important to note that hybridization occurs to optimize the overlap of atomic orbitals and allow for the maximum stability of the molecule. In the case of sulfuric acid, sp³ hybridization is the most energetically favorable arrangement, as it maximizes the bonding interactions and minimizes electron repulsions between the sigma bonds and lone pairs of electrons on the oxygen atoms.
Therefore, the sp³ hybridization of sulfur in sulfuric acid is a result of the electronic structure and the requirement for the formation of four sigma bonds around the sulfur atom.