Isotopes of hydrogens

Different atoms of the same element with the same atomic number but different mass numbers are known as isotopes. Hydrogen has three isotopic forms ( Protium, Deuterium, and Tritium): with mass numbers 1,2, and 3. Because the amount of neutrons in each isotope varies, the mass number of the isotopes varies as well. Isotopes have different mass numbers due to the difference in neutron numbers.

isotopes of hydrogen

The most abundant and stable isotope is protium (11H) or ordinary hydrogen.

A stable isotope is a deuterium (12H or D), also called heavy hydrogen.

The third isotope is radioactive (t1/2 = 13.33yrs) in nature which is tritium (13H or T) Tritium is a β-particle emitter.

Comparative study of 3 isotopes

Name Hydrogen(Protium)DeuteriumTritium
Symbol11H or H12H or D13H or T
Atomic number (Z)111
Mass number (A)1.007992.01473.0170
Number of protons (P)111
Number of electrons (e)111
Number of neutrons (n)012
Relative abundance99.985%0.015%10-15%
Nuclear spin1/211
Molecular formulaH2D2T2

All the three isotopes of hydrogen have the same electronic configuration (1s1). So, all three isotopes give similar chemical properties. However, due to different mass numbers, they are different in their physical properties and in the rates of a chemical reaction. For example, electrolysis of ordinary water occurs more rapidly than in heavy water. This difference in properties due to the difference in mass number is called the isotope effect. Hence ordinary hydrogen undergoes reactions faster than deuterium due to the isotopes effect.

Physical constantsH2D2T2
Molecular mass (g mol-1)2.0164.0286.03
Melting point (K)13.818.720.63
Boiling point (k)20.423.925.0
Bond energy (KJ mol-1at 298L) 435.9443.4446.9
Heat oof vaporization KJ mol-1 0.9041.2261.393

Applications of Isotopes of Hydrogen


  • Used to produce oxy-hydrogen flame for welding
  • Used in filling balloons
  • Used in Haber’s process of ammonia synthesis
  • used in the manufacture of vanaspati ghee.
  • Used in reducing agents in metallurgical process.


  • Used in the transformation of nuclear reaction as deuteron projectile.
  • deuterium and its compounds are used as tracers to study reaction mechanisms.
  • Used in nuclear fusion reactions.


  • Used in nuclear reaction to liberate large amount of heat which is used in a hydrogen bomb.
  • It is a radioactive isotope used as a radioactive tracer in water absorption by plant roots.


Isotopes of hydrogen with 2 neutrons is called…

Tritium has 2 neutrons.

What are the three isotopes of hydrogen?

The three isotopes of hydrogen protium, deuterium, and tritium.

How do isotopes of hydrogen differ from one another?

In isotopes of hydrogen, the amount of neutrons and the mass number varies from one another.

How many isotopes of hydrogen are known?

3 types of hydrogen are known.

Heavy isotopes of hydrogen?

Deuterium is a heavy isotope of hydrogen.

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