Deuterium and tritium are:

The correct answer is Isotopes of Hydrogen.

Key Points

• Deuterium and tritium are Isotopes of Hydrogen.
• Isotopes are different forms of the same element that contain an equal number of protons but different numbers of neutrons in their nuclei, and hence differ in relative atomic mass but not in chemical properties.
• Hydrogen has three isotopes: Hydrogen (1 proton and 0 neutrons), Deuterium (1 proton and 1 neutron) and Tritium (1 proton and 2 neutrons).
• Out of the three, tritium is a very rare isotope and is also radioactive.

Additional Information

• ISOTOPES:
  • Atoms with the same number of protons but different numbers of neutrons are called isotopes.
  • They are elements with the same atomic number but different mass numbers since the atomic number equal the number of protons and the atomic mass equal the sum of protons and neutrons.
  • Isotopes are various forms of the same element.
  • Protium 1H1, deuterium 1H2 or D, and finally tritium 1H3 or T are the three hydrogen isotopes.
  • There are no neutrons in protium, but one neutron is present in deuterium and two neutrons are present in tritium.
  • Protium is the most common type of hydrogen, with deuterium accounting for 0.0156 per cent of all hydrogen on the planet's surface.
  • The concentration of tritium is one atom per 1018 protium atoms.
  • The only tritium, out of these three hydrogen isotopes, is radioactive in nature and releases low-energy b particles.