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Radioactive Hydrogen Isotope

April 15, 2013

Introduction to radioactive hydrogen isotope:

In the periodic table, Hydrogen is the first chemical element with atomic number 1. Hydrogen element is represented by the symbol H. Hydrogen has an average atomic weight of 1.00794 u (1.007825 u for Hydrogen-1), hydrogen is the lightest and most abundant chemical element, constituting roughly 75 % of the Universe’s elemental mass. Stars in the main sequence of the universe are mainly composed of hydrogen in its plasma state. Naturally occurring elemental hydrogen is found relatively rare on Earth.

Isotopes of Hydrogen

The most common hydrogen isotope is protium (name rarely used, symbol 1H) with a single proton and without any neutrons. In ionic compounds it can take both negative charge (an anion known as a hydride and written as H), as well as positive charge H+.

Hydrogen (H) has three naturally occurring isotopes, which are denoted as 1H, 2H, and 3H. Other, highly unstable nuclei, from 4H to 7H, have been synthesized in the laboratory but not observed naturally.

Only Hydrogen is the element that has got different names for its isotopes in common use today. The 2H (or H-2) isotope is usually called deuterium, while the 3H (or H-3) isotope is usually named as tritium. The symbols D and T (instead of 2H and 3H) are commonly used for deuterium and tritium.

Radioactive hydrogen isotopes

Hydrogen-1 (protium):

1H,  protium is the most common hydrogen isotope with an abundance of more than 99.980%. Because the nucleus of this isotope consists of only a single proton, descriptively named as protium.

Hydrogen-2 (deuterium):

2H, the simple and stable hydrogen isotope, is known as deuterium represented by the symbol D and contains one proton and one neutron in its nucleus. Deuterium is not radioactive hydrogen isotope, and does not represent any significant toxicity hazards. Water which is enriched in molecules that include deuterium instead of normal hydrogen is called heavy water or deuterated water. Deuterium and its compounds are used as a non-radioactive label in chemical experiments and in solvents for decoupling of 1H-NMR spectroscopy.

Hydrogen-3 (tritium):

3H, tritium contains one proton and two neutrons in its nucleus. It is a radioactive hydrogen isotope, decaying into helium-3 through β− decay with a half-life of 12.33 years. Small amounts of tritium exist in nature because of the interaction of cosmic rays with atmospheric gases. Tritium has also been released during nuclear weapon testing and experiments.

  • It is used in the thermonuclear fusion weapons.
  • As a tracer in isotope geochemistry and also is specialized in self-powered lighting devices.

The most common method by which tritium is produced is by bombarding a natural isotope of lithium, lithium-6, with neutrons in a nuclear reactor.

Hydrogen-4 (quadrium):

4H, quadrium is a highly unstable isotope of hydrogen. The nucleus consists of 1 proton and 3 neutrons. It has been synthesized in the laboratory by bombarding tritium with fast-moving deuterium nuclei. In this experiment, the tritium nuclei capture the bombarded neutron from the fast-moving deuterium nucleus. The presence of the hydrogen-4 was determined by detecting the emitted protons. The atomic mass of quadrium is 4.02781 ± 0.00011. It decays through neutron emission reaction with a half-life of (1.39 ± 0.10) × 10−22 seconds.


5H or H-5 is a highly unstable radioactive hydrogen isotope. The nucleus consists of 1 proton and 4 neutrons. It has been synthesized in the laboratory by the bombardment of tritium with fast-moving tritium nuclei. In this experiment, one of the tritium nuclei captures two neutrons from the other, converting into a nucleus with one proton and four neutrons. The existence of hydrogen-5 is deduced by determining the remaining proton. H-5 decays through double neutron emission and the reaction has a half-life of at least 9.1 × 10−22 seconds.


6H or H-6 is made of one proton and 5 neutrons. 6H or H-6 is also radioactive hydrogen isotope. 6H or H-6 decays through triple neutron emission and the reaction has a half-life of 3×10−22 seconds. It consists of 1 proton and 5 neutrons.


7H or H-7 consists of one proton and 6 neutrons. This isotope was first synthesized in 2003 by a group of Russian, Japanese and French scientists at RIKEN’s RI Beam Science Laboratory by bombarding a hydrogen with helium-8 atoms. In this reaction, the neutrons from helium-8 were donated to the hydrogen’s nucleus.


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