Tritium is an isotope of the chemical element hydrogen. It has not only a single proton but also two neutrons in the nucleus of its atoms. Although technically it is still the element hydrogen, it has its own chemical symbol, T. Chemically, tritium reacts in exactly the same manner as hydrogen, although slightly slower because of its greater atomic weight. A tritium atom has almost three times the mass of a regular hydrogen atom: the atomic weight of tritium is 3.016 whereas the atomic weight of hydrogen is 1.008. Tritium is radioactive, with a half-life of 12.26 years. Its nucleus emits a low-energy beta particle, leaving behind an isotope of helium, helium-3, that has a single neutron in its atomic nucleus. (The common isotope of helium, helium-4, contains two neutrons in its atomic nucleus.) No gamma rays, which are high-energy electromagnetic radiation, are emitted in the decay of tritium, so the...