* Atoms are the fundamental building blocks of matter. They are the smallest unit of an element that retains the chemical properties of that element.

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

* Molecules are formed when two or more atoms bond together. These atoms can be of the same element (like O₂ for oxygen gas) or different elements (like H₂O for water).

So, while a molecule can be made up of more than one type of atom, a single atom is always a single type of atom.