What is the molecular formula for sulfur trioxide?

The molecular formula for sulfur trioxide is represented as SO3. This formula indicates that each molecule of sulfur trioxide consists of one sulfur atom and three oxygen atoms.

In chemical nomenclature, the prefix “tri-” signifies that there are three oxygen atoms attached to the sulfur atom. Therefore, the name sulfur trioxide directly corresponds to the molecular formula SO3. Each element's symbol in the formula represents the number of atoms; "S" refers to sulfur and "O" for oxygen. As there is one sulfur and three oxygens, the formula accurately reflects the composition stated in the name.

Other options do not accurately represent the correct number of sulfur and oxygen atoms that would correspond to the name sulfur trioxide. For instance, SO2 would be sulfur dioxide, indicating only two oxygen atoms, and S2O3 would suggest two sulfur atoms and three oxygen atoms, which is not aligned with the name sulfur trioxide. Similarly, S3O2 would imply three sulfur atoms and only two oxygen atoms, which again does not match the expectations from the name given. Thus, the correct answer, SO3, is precisely aligned with its nomenclature.