Atoms are the smallest unit of an element that retains the chemical properties of that element. They are made up of even smaller particles:

* Protons: Positively charged particles found in the nucleus of an atom.

* Neutrons: Neutrally charged particles also found in the nucleus.

* Electrons: Negatively charged particles that orbit the nucleus in shells.

The arrangement and number of these subatomic particles determine the properties of each element and the substances they form.