Final answer:
Sulfur appears first in the compound name SF4 because it is the less electronegative element, positioned lower on the periodic table compared to elements such as oxygen, and thus is the central atom in the molecule.
Step-by-step explanation:
In naming compounds like SF4, the rules of chemical nomenclature dictate that the less electronegative element is listed first, which here is sulfur. Sulfur is lower on the periodic table than oxygen and falls into Group 6A. While both sulfur and oxygen reside in the same group, sulfur appears in Row 3 whereas oxygen is in Row 2, meaning sulfur has a larger atomic radius and generally a lower electronegativity relative to oxygen.
The name sulfur tetrafluoride comes from the combination of the central sulfur atom and the four fluorine atoms it bonds with. The Lewis structure of SF4 reveals four single bonds and one lone pair of electrons on the sulfur atom, confirming sulfur's central position in the molecule. Additionally, the formal charge principles support that sulfur, with its six valence electrons, should serve as the central atom in such compounds like sulfur dioxide and sulfur tetrafluoride.