An atom is the smallest unit of matter, which cannot be divided any further. An atom can also be defined as the smallest particle of an element that takes part in a chemical reaction. The simple relationship between atoms and ions is that ions are also atoms, but only when the number of protons and that of electrons are not equal.
An atom consists of protons, neutrons, and electrons. The nucleus of an atom consists of both the proton and neutron, whereas electrons orbit the nucleus. If there are more electrons in an atom compared to the number of protons, the ion is known as an anion.
But if there are more protons in an atom compared to the number of electrons, the ion is action. One of the major differences between atom and ion is that ions don't take part in chemical reactions, whereas atoms usually take part in chemical reactions.