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All elements have atoms as their basic unit and an atom contains its three fundamental particles that are negative charged electrons, positive charged protons, and neutral particles neutrons. The number of protons and neutrons which are present in the nucleus is called the mass number of elements while the number of protons is called the atomic number. The same elements whose atoms contain the same number of protons but different numbers of neutrons are called isotopes.

We can take a simple example of hydrogen atoms which has its three isotopes. These are hydrogen with zero neutrons, deuterium contains one neutron, and tritium contains two neutrons. Here we are discussing about the isotope of hydrogen that is deuterium which is known as heavy hydrogen. How this isotope is useful, what is its mass and other properties, let’s discuss about that.


What is Deuterium?

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Hydrogen normally has three isotopes with deuterium one among them. Deuterium is a isotope of hydrogen which varies from hydrogen by one neutron normally hydrogen has only one proton, where as deuterium has one proton and one neutron. It has wide applications in fission reactors. The chemical symbol of deuterium is 2H and is denoted by "D".

Heavy Hydrogen

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Heavy hydrogen is the name given to either of the higher isotopes of hydrogen 1 like deuterium and tritium. But this name is especially used for deuterium. Its atomic mass is about 2 and has 1 proton and 1 neutron in its nucleus. So its mass is double the mass of normal hydrogen. The extra neutron in deuterium makes it heavier than normal hydrogen; hence it is called heavy hydrogen. Tritium has an atomic mass of 3 and has 1 proton and 2 neutrons inside the nucleus. Both have the same atomic number as they are isotopes of hydrogen.

Heavy Hydrogen was discovered by Harold Urey. He also won Nobel Prize for chemistry in 1934. He predicted difference between the vapor pressures of molecular hydrogen (H2) and of a corresponding molecule with one hydrogen atom replaced by deuterium (HD) and thus the possibility of separating these substances by distillation of liquid hydrogen. The deuterium was detected in the residue of a distillation of liquid hydrogen. It was prepared in pure form by G.N. Lewis by using electrolytic method of concentration. When water is electrolyzed, hydrogen gas is produced which contains a small amount of deuterium, therefore deuterium is concentrated in water. When the amount of water has been reduced to about one hundred-thousandth of its original volume by continued electrolysis, nearly pure deuterium oxide known as heavy water is secured. This method of preparing heavy water was used in World War II.

Deuterium Water

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Deuterium Water also known as heavy water is similar to normal water. It is formed by combination of heavy hydrogen i.e. deuterium and oxygen and is denoted by D2O. Deuterium water is more viscous than normal water. Heavy water is denser than normal water by 10.6% such that ice of heavy water sinks in normal water. Heavy water behaves as toxic for some animals, while some animals can survive in heavy water but they grow slowly as compared to normal water.

Deuterium Water is non radioactive. Human body contains about 5 grams of deuterium naturally and it is harmless. If heavy water is ingested in large quantities ( such that about 50% of water in body becomes heavy water) than it can cause cell dysfunction and can ultimately result in death.
If compared with light water heavy water exhibit following differences:
  • Freezing point of heavy water is 3.82oC while that of light water is 0oC.
  • Its boiling point is 101.4oC and that of normal water is 100C.
  • Density of heavy water is 1.1056 g/ mL and of normal water is 0.9982 g/ mL.
  • Its pH or pD is 7.43 and of light water is 6.9996.
  • There is slightest difference in the taste and smell of light and heavy water.
Deuterium Water effects on biological systems: Heavy water behaves as toxic for some animals, while some animals can survive in heavy water but they grow slowly as compared to normal water. Enzymes rely on their finely tuned networks of hydrogen bonds to perform their tasks. Since a hydrogen bond with deuterium is slightly stronger than that involved with ordinary hydrogen, some normal reactions in cells are disrupted in a highly deuterated environment. Particularly hard-hit by heavy water, plants stop growing and seeds do not germinate.

It has been proposed by an institute in Moscow that while large amount of heavy water is harmful, low doses of heavy water increases life span by upto 30%. High doses of deuterium water in animals can cause sterility and can cause death also for some animals at 50%, like rats and for some at 90% of heavy water consumption like fish, tadpoles, flatworms. In humans to produce any noticeable toxic effects, large amounts of heavy water would need to be ingested without normal water intake for many days.

Applications of Deuterium Water :
  1. Deuterium Water is used in nuclear magnetic resonance spectroscopy.
  2. It is also used in fourier transform spectroscopy for collecting FTIR spectra of proteins in solution.
  3. Deuterium Water is used in nuclear reactors where it is used as moderator to slow down the speed of neutrons so that they can react with Uranium 235 and then with U 238.
  4. It is also used in nuclear weapons.
  5. It is used to produce tritium. It is created in heavy water moderators where deuterium captures a neutron thereby producing tritium.
  6. It is also used for metabolic rate testing in humans where it is used in a mixture with H218O.
  7. It is also used as coolant for nuclear reactors.

Is Deuterium Radioactive?

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Deuterium is stable isotope of hydrogen. It is non - radioactive, and does not have a significant toxicity hazard. Normal water that is enriched in molecules that have deuterium instead of normal hydrogen is called heavy water.
In chemical experiments and in solvents for 1H-NMR spectroscopy, deuterium and its compounds are used as a non-radioactive label. Heavy water is used as moderator and coolant for nuclear reactors. For commercial nuclear fusion, deuterium is also a potential fuel.

Deuterium Half Life : Deuterium is a stable atom. It is at least as stable as the proton contained in it. Theoretical considerations propose that the proton may have a very long half-life. Protons have not been observed to decay though experimentally. Lower bound on the proton's half-life thereby established is about 1035 years.

Deuterium and Tritium

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Deuterium and tritium both are isotopes of hydrogen. They both have same atomic number. Only difference between them is that they have different number of neutrons. Deuterium has 1 and tritium has 2 neutrons. Another isotope of hydrogen is Protium. Both protium and deuterium are stable but tritium is unstable.

Deuterium is denoted by 2H or D and tritium is denoted by 3H or T.

Deuterium is not radioactive in nature but tritium is radioactive isotope. Hence tritium is harmful and dangerous.

Deuterium has 1 proton and 1 neutron while tritium has 1 proton and two protons. Therefore atomic number of both is same as they are isotopes while their mass number is 2 for deuterium and 3 for tritium. Nucleus of deuterium is called deuteron and that of tritium is called Triton.

Tritium is found rarely on Earth naturally in trace amounts and is formed naturally by interaction of the atmosphere with cosmic rays. Deuterium has a natural abundance of about 0.0156% in Earth’s ocean. It occurs in trace amount as deuterium gas naturally. But most natural occurrence is bonded with a typical 1H atom which is a gas, called Hydrogen Deuteride.

Isotopic mass of tritium is 3.0160492 u and that of deuterium is 2.014102 u.

Deuterium has stable half life as it is stable isotope while half life of tritium is 12.32 years.

Excess energy of deuterium is 13,135.720 $\pm$ 0.001 keV and that of tritium is 14,949.794 $\pm$ 0.001 keV.

Binding energy for tritium nucleus is 8,481.821$\pm$ 0.004 keV and for deuterium is 2,224.52 $\pm$ 0.20 keV.

Deuterium’s spin is +1 and that of tritium is + ½.

Tritium combines with oxygen and forms a liquid known as tritiated water (THO). Deuterium combines with oxygen to form D2O. D2O is also known as Heavy Water and is more viscous than water.

Tritium is harmful for human health. Tritiated water present in water above regulatory limits is also harmful for human. Tritium is a beta emitter of low energy, hence it is not harmful externally but it is hazardous if inhaled or ingested through food or absorbed via skin. Deuterium is not hazardous to health but can be used to form nuclear weapons.

Tritium is artificially produced from lithium, deuterium, fission, cosmic rays and 3He. Deuterium is not artificially produced as it is present naturally in abundance in Earth’s ocean and can serve many human generations. It is extracted from ocean using centrifuge process.

Tritium and deuterium combines to form Helium and produces large amount of energy of about 17.6 MeV. Their chemical reaction is as follows:
3T + 1D → 4He + n

Applications of Tritium and Deuterium:
Tritium can be used for the following:
  1. The electrons produced from the radioactive decay of tritium cause glowing of phosphor. So it can be used to make self powered lighting devices such as betalights. These are used in watches, map lights, firearm night sights.
  2. It is used in nuclear weapons for enhancing the efficiency and yield of fission bombs. It is also used in hydrogen bombs at fission stages.
  3. It is also used in hydrogen bombs. It is used as fuel for controlled nuclear fusion.
  4. Tritium is used as a transient tracer. It has the ability to outline oceans’ biological, chemical and physical paths due to its evolving distribution.
Deuterium is used in many areas as follows:
  1. It is used in nuclear fusion reactions. For example in deuterium tritium reaction where it produces large amount of energy .
  2. T + 1D 4He + n
  3. Deuterium is used as a stable tracer in chemistry and environmental science. It can be used to trace the geographic origin of earth’s water.
  4. It is used in NMR spectroscopy, also useful in nuclear resonance spectroscopy such as proton NMR.
  5. It is also used in making thermonuclear weapons.
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