Sulfide is an ion, not an element. It's formed when sulfur gains two electrons.

The atomic number of sulfur (the element) is 16. The atomic number tells you the number of protons in an atom's nucleus.

Since sulfide is an ion (S²⁻), it still has the same number of protons (16) as a neutral sulfur atom. However, it has gained two electrons, giving it a charge of -2.