Atoms are made up of three subatomic particles. These are protons, electrons and neutrons. Protons are POSitivly charged. Neutrons are NEUtral. Electrons are negative (electic shocks are bad). The nucleus (or centre) of an atom is made up of protons and neutrons, and electrons orbit the nucleus. You can roughly think of this as the nucleus being the sun in our solar system and planets as electrons. The combination of these subatomic particles can determin the element, relative atomic mass and charge of the atom/ion.