The three types of particles that make up atoms are protons, neutrons, and electrons. Protons and neutrons are found in the nucleus of the atom, while electrons orbit the nucleus. Protons have a positive charge, electrons have a negative charge, and neutrons have no charge. The number of protons in an atom determines its atomic number, which identifies the element. The number of neutrons in an atom can vary, giving rise to different isotopes of the same element.