The isotopes of hydrogen known as deuterium and tritium are distinguished by their atomic structure. Deuterium, or H-2, contains one proton and one neutron, while tritium, or H-3, contains one proton and two neutrons. These isotopes are important in various scientific applications, including nuclear fusion research and as tracers in chemical reactions. Deuterium is stable, while tritium is radioactive with a half-life of about 12.3 years. Their unique properties make them valuable in both academic studies and practical applications.