Final answer:
The molecular shapes of xenon tetroxide and sulfur trioxide are influenced by their central atoms' ability to form certain hybridized orbitals. Hybridization and the involvement of d orbitals are not always necessary for larger atoms, as electron pairs are farther from the nucleus, reducing the need for hybridized orbitals to explain observed molecular geometries.
Step-by-step explanation:
The question pertains to why certain molecules, such as xenon tetroxide (XeO4) and sulfur trioxide (SO3), exhibit certain molecular shapes despite having multiple double bonds and, in the case of sulfur trioxide, a hypervalent sulfur atom.
Previously, it was believed that the π-bonds in these molecules might be made from the overlap of d orbitals of the central atom with the p orbitals of the oxygen atoms.
However, hybridization is not always necessary to explain the molecular geometries of compounds with larger central atoms because valence electron pairs are farther from the nucleus, and d orbitals may not be involved as once thought.
For example, xenon tetroxide exhibits a tetrahedral geometry consistent with sp3 hybridization despite the presence of double bonds. Sulfur-containing compounds can be less hybridized than analogous oxygen compounds, as evidenced by the smaller bonding angles in compounds like H2S as compared to H2O.
When addressing molecules with larger central atoms and higher periods, the need for invoking the use of d orbitals for bonding decreases. Molecules with trigonal planar electron domain geometry like sulfur trioxide typically form sp2 hybrid orbitals, not involving d orbitals for π-bonding.