Protons, neutrons and electrons are the fundamental particles that make up atoms. Protons have a positive charge and are found in the atom's nucleus along with neutrons, which have no charge. The number of protons determines what element the atom is. Electrons have a negative charge and orbit around the nucleus.
Each element is defined by its number of protons. The number of neutrons can vary which creates different isotopes of an element. For example, all carbon atoms have 6 protons but some carbon atoms have 6 neutrons and some have 7. Protons and neutrons are made up of even smaller particles called quarks. Protons contain 2 up