Here's why:

* Group Number: The group number of an element in the periodic table directly corresponds to the number of valence electrons.

* Valence Electrons: These are the electrons in the outermost energy level, which are responsible for chemical bonding and reactivity.

* Sulfur's Electron Configuration: Sulfur has an electron configuration of [Ne] 3s² 3p⁴. This means it has 6 electrons in its third energy level (3s² and 3p⁴).

Therefore, sulfur, with its six valence electrons, fits the definition of a Group 16 element.