The number of protons in an atom determines the element (C). These protons reside in the nucleus of the atom. These elements are listed on the periodic table. Each element on the periodic table has a different atomic number or number of protons in the nucleus of an atom. Protons, neutrons and electrons are the three main particles that make up an atom. Protons are positively charged, electrons are negatively charged and neutrons are neutral i.e. they have no charge. In order to find the number of protons, neutrons and electrons in an atom, you can look up this information on the periodic table.