Here's why:

* Elements are made up of only one type of atom. For example, gold is made up of only gold atoms.

* Compounds are formed by the chemical combination of two or more different types of atoms. For example, water (H₂O) is made up of hydrogen and oxygen atoms.

While atoms are the smallest units of elements and compounds, they can be further broken down into subatomic particles like protons, neutrons, and electrons. However, these subatomic particles don't have the same chemical properties as the original atom.