Here's why:

* Elements are the simplest form of matter and cannot be broken down further. Examples include sulfur (S) and oxygen (O).

* Compounds are formed when two or more elements combine chemically in a fixed ratio.

* Anions are negatively charged ions. Sulfide (S²⁻) is a negatively charged ion formed when sulfur gains two electrons.

Sulfide is a part of many compounds, such as:

* Hydrogen sulfide (H₂S), a gas with a rotten egg smell

* Iron sulfide (FeS), found in minerals

* Sodium sulfide (Na₂S), used in various industrial processes

So, sulfide is not an element or a compound in itself, but rather a negatively charged ion that forms part of many compounds.