Tritium heavier atoms. The tritium nucleus, containing one proton and two neutrons, has the same charge as the nucleus of ordinary hydrogen, and it experiences the same electrostatic repulsive force when brought close to another atomic nucleus. However, the neutrons in the tritium nucleus increase the attractive strong nuclear force when brought close enough to another atomic nucleus. As a result, tritium can more easily fuse with other light atoms, compared with the ability of ordinary hydrogen to do so. The same is true, albeit to a lesser extent, of deuterium. This is why brown dwarfs (so-called failed stars) cannot utilize
Hydrogen isotope biogeochemistry as a relatively weak beta reaction, so the radioactivity cannot permeate skin. Tritium is thus only hazardous if directly ingested or inhaled. Protium is a spin 1/2 subatomic particle and is therefore a fermion. Other fermions include neutrons, electrons, and the radioactive isotope tritium. Fermions are governed by Pauli's exclusion principle, where no two particles can have the same quantum number. However, bosons like deuterium and photons, are not bound by exclusion and multiple particles can occupy the same energy state. This fundamental difference in H and H manifests in many physical properties. Integer spin particles like deuterium follow Bose-Einstein