Chlorine, sulfur and copper are elements – they have fixed physical and chemical properties, and cannot be broken down into simpler substances.
(Images: W. Oelen, Wikimedia Commons; Ben Mills, Wikimedia Commons; Jonathan Zander, Wikimedia Commons)
Copper sulfate is a compound – it has fixed physical and chemical properties, but can be broken down into simpler substances (the elements copper, sulfur and oxygen).
(Image: Stephanb, Wikimedia Commons)