Atoms and elements are both pure substances. This means that they cannot be broken down into simpler parts and that their composition (what they are made of) never changes.
Atoms are made of three different subatomic particles: protons, neutrons, and electrons. The protons and neutrons are housed within the nucleus of an atom. The electrons are located orbiting the nucleus in either an electron cloud or orbital.
Elements are specific kinds of atoms. Each element is defined by its number of protons. If the number of electrons changes within an element, then an ion (charged atom) of that element is created. If the number of neutrons changes within an element, then an isotope is formed. But if the number of protons changes, then that atom has just become a different element.