Here's why:

* Elements are the simplest pure substances. They are made up of only one type of atom. For example, gold (Au) is an element, and it's made up of only gold atoms.

* Compounds are made up of two or more different elements chemically combined. For example, water (H₂O) is a compound made of hydrogen (H) and oxygen (O) atoms. Compounds can be broken down into their constituent elements through chemical reactions.

Let me know if you have any more questions!