Science of emergence as demonstrated by the periodic table of chemical elements describes hydrogen with only two known isotopes in addition to ordinary hydrogen. The nucleus of ordinary hydrogen has one proton. The nucleus of isotope deuterium is called deuteron. It is composed of one proton and one neutron. The nucleus of isotope tritium is called triton. It is composed of one proton and two neutrons. Since masses of proton and neutron are practically equal, mass number notations are used for these isotopes respectively as hydrogen-1, hydrogen-2, and hydrogen-3. However, hydrogen isotope with mass number 4 which should be composed of 1-proton and 3-neutron does not exist naturally, not even artificially at this time. The next element with mass number of 4 is helium. But it is composed of 2-proton and 2-neutron. Helium nuclei are usually called alpha particles which are one of the three components of radioactivity: alpha, beta, and gamma radiations. Betas are just energetic electrons, and gammas are high frequency or short wavelength photons.