how to know if a substance is a compound
A chemical element bonded to an identical chemical element is not a chemical compound since only one element, not two different elements, is involved. Examples are the diatomic molecule hydrogen (H 2) and the polyatomic molecule sulfur (S 8).he physical and chemical properties of compounds differ from those of their constituent elements. This is one of the main criteria that distinguish a compound from a mixture of elements or other substancesâin general, a mixture's properties are closely related to, and depend on, the properties of its constituents.