* Elements are pure substances that cannot be broken down into simpler substances. Examples include gold, silver, and copper.

* Compounds are formed when two or more elements chemically combine in a fixed ratio. Examples include water (H₂O) and salt (NaCl).

Coins are typically made of alloys, which are mixtures of metals. For instance, a US penny is primarily made of zinc with a thin layer of copper plating. This means it's a combination of different elements, not a pure element or a chemically combined compound.

Key takeaway: Coins are mixtures because they consist of multiple substances that are not chemically bonded together.