two extra neutrons and no extra electron 12C and 14C  are the two isotopes of carbon atom that have same atomic number, but different mass numbers. This means that they have same number of protons and electrons, but different number of neutrons. Therefore,  12C has 6 protons, 6 electrons and 6 neutrons, whereas ​ 14C has 6 electrons, 6 protons and 8 neutrons.