Skip to main content
Select Source:

deuterium

deuterium (dōōtēr´ēəm), isotope of hydrogen with mass no. 2. The deuterium nucleus, called a deuteron, contains one proton and one neutron. Deuterium is also called heavy hydrogen, and water in which the hydrogen atoms are deuterium is called heavy water (deuterium oxide, D2O). Deuterons are sometimes used in particle accelerators, and heavy water is used in "swimming pool" nuclear reactors as a moderator.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"deuterium." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. 20 Nov. 2018 <https://www.encyclopedia.com>.

"deuterium." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. (November 20, 2018). https://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/deuterium

"deuterium." The Columbia Encyclopedia, 6th ed.. . Retrieved November 20, 2018 from Encyclopedia.com: https://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/deuterium

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

deuterium

deuterium Isotope (D or H2) of hydrogen whose nuclei contain a neutron in addition to a proton. Deuterium occurs in water as D2O (heavy water), from which it is obtained by electrolysis. Heavy water is used in some nuclear reactors as a moderator that slows down free neutrons to increase nuclear fission. Properties: r.a.m. 2.0144.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"deuterium." World Encyclopedia. . Encyclopedia.com. 20 Nov. 2018 <https://www.encyclopedia.com>.

"deuterium." World Encyclopedia. . Encyclopedia.com. (November 20, 2018). https://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/deuterium

"deuterium." World Encyclopedia. . Retrieved November 20, 2018 from Encyclopedia.com: https://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/deuterium

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

deuterium

deu·te·ri·um / d(y)oōˈti(ə)rēəm/ • n. Chem. a stable isotope of hydrogen with a mass approximately twice that of the usual isotope. (Symbol: D)

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"deuterium." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. 20 Nov. 2018 <https://www.encyclopedia.com>.

"deuterium." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. (November 20, 2018). https://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/deuterium

"deuterium." The Oxford Pocket Dictionary of Current English. . Retrieved November 20, 2018 from Encyclopedia.com: https://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/deuterium

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

deuterium

deuterium (chem.) an isotope of hydrogen. symbol D. XX. f. Gr. deúteros (cf. next) + -IUM.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"deuterium." The Concise Oxford Dictionary of English Etymology. . Encyclopedia.com. 20 Nov. 2018 <https://www.encyclopedia.com>.

"deuterium." The Concise Oxford Dictionary of English Etymology. . Encyclopedia.com. (November 20, 2018). https://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/deuterium-0

"deuterium." The Concise Oxford Dictionary of English Etymology. . Retrieved November 20, 2018 from Encyclopedia.com: https://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/deuterium-0

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

Deuterium

Deuterium

Discovery

Ureys search for deuterium

Properties and preparation

Uses

Fusion reactions

Resources

Deuterium is an isotope of hydrogen (H) with atomic mass of 2. It is represented by the symbols2H or D. Deuterium is also known as heavy hydrogen. The nucleus of the deuterium atom, consisting of a proton and a neutron, is known as a deuteron and is represented in nuclear equations by the symbol d.

Discovery

The possible existence of an isotope of hydrogen with atomic mass of two was suspected as early as the late 1910s after British chemist Frederick Soddy (18771956) had developed the concept of isotopes. Such an isotope was of particular interest to chemists. Since the hydrogen atom is the simplest of all atoms consisting of a single proton and a single electronit is the model for most atomic theories. An atom just slightly more complexone that contains a single neutronalso could potentially contribute valuable information to existing atomic theories.

Among those who sought for the heavy isotope of hydrogen was Harold Urey (18931981), at the time professor of chemistry at Columbia University. Urey began his work with the realization that any isotope of hydrogen other than hydrogen-1 (also known as protium) must exist in only minute quantities. The evidence for that fact is that the atomic weight of hydrogen is only slightly more than 1.000. The fraction of any isotopes with mass greater than that value must, therefore, be very small. Urey designed an experiment, therefore, that would allow him to detect the presence of heavy hydrogen in very small concentrations.

Ureys search for deuterium

Ureys approach was to collect a large volume of liquid hydrogen and then to allow that liquid to evaporate very slowly. His hypothesis was that the lighter and more abundant protium isotope would evaporate more quickly than the heavier hydrogen-2 isotope. The volume of liquid hydrogen remaining after evaporation was nearly complete would be relatively rich in the heavier isotope.

In the actual experiment, Urey allowed 4.2 qt (4 l) of liquid hydrogen to evaporate until only 0.034 oz (1 ml) remained. He then submitted that sample to analysis by spectroscopy. In spectroscopic analysis, energy is added to a sample. Atoms in the sample are excited and their electrons are raised to higher energy levels. After a moment at these higher energy levels, the electrons return to their ground state, giving off their excess energy in the form of light. The bands of light emitted in this process are characteristics for each specific kind of atom.

By analyzing the spectral pattern obtained from his 0.034-oz (1-ml) sample of liquid hydrogen, Urey was able to identify a type of atom that had never before been detected, the heavy isotope of hydrogen. The new isotope was soon assigned the name deuterium. For his discovery of the isotope, Urey was awarded the 1934 Nobel Prize in chemistry.

Properties and preparation

Deuterium is a stable isotope of hydrogen with a relative atomic mass of 2.014102 compared to the atomic mass of protium, 1.007825. Deuterium occurs to the extent of about 0.0156%deg; in a sample of naturally occurring hydrogen. Its melting point is -426 °F(-254°C)compared to -434°F (-259°C) for protiumand its boiling point is -417°F (-249°C) compared to -423°F (-253°C) for protium. Its macroscopic properties of color, odor, taste, and the like are the same as those for protium.

Compounds containing deuterium have slightly different properties from those containing protium. For example, the melting and boiling points of heavy water are, respectively, 38.86°F (3.81°C) and 214.56°F (101.42°C). In addition, deuterium bonds tend to be somewhat stronger than protium bonds. Thus chemical reactions involving deuterium-containing compounds tend to go more slowly than do those with protium.

Deuterium is now prepared largely by the electrolysis of heavy water, that is, water made from deuterium and oxygen (D2 O). Once a great rarity, heavy water is now produced rather easily and inexpensively in very large volumes.

Uses

Deuterium has primarily two uses, as a tracer in research and in thermonuclear fusion reactions. A tracer is any atom or group of atoms whose participation in a physical, chemical, or biological reaction can be easily observed. Radioactive isotopes are perhaps the most familiar kind of tracer. They can be tracked in various types of changes because of the radiation they emit.

Deuterium is an effective tracer because of its mass. When it replaces protium in a compound, its presence can easily be detected because it weights twice as much as a protium atom. In addition, as mentioned above, the bonds formed by deuterium with other atoms are slightly different from those formed by protium with other atoms. Thus, it is often possible to figure out what detailed changes take place at various stages of a chemical reaction using deuterium as a tracer.

Fusion reactions

Scientists now theorize that energy produced in the sun and other stars is released as the result of a series of thermonuclear fusion reactions. The term fusion refers to the fact that two small nuclei, such as two hydrogen nuclei, fuseor join togetherto form a larger nucleus. The term thermonuclear means that such reactions normally occur only at very high temperatures, typically a few millions of degrees Celsius. Interest in fusion reactions arises not only because of their role in the manufacture of stellar energy, but also because of their potential value as sources of energy on Earth.

Deuterium plays a critical role in most thermonu-clear fusion reactions. In the solar process, for example, the fusion sequence appears to begin when two protium nuclei fuse to form a single deuteron. The deuteron is used up in later stages of the cycle by which four protium nuclei are converted to a single helium nucleus.

In the late 1940s and early 1950s scientists found a way of duplicating the process by which the suns energy is produced in the form of thermonuclear fusion weapons, the so-called hydrogen bomb. The detonating device in this type of weapon was lithium deuteride, a compound of lithium metal and deuterium. The detonator was placed on the casing of an ordinary fission (atomic) bomb. When the fission bomb detonated, it set off further nuclear reactions in the lithium deuteride which, in turn, set off fusion reactions in the larger hydrogen bomb.

KEY TERMS

Deuteron A proton and a neutron; the nucleus of a deuterium atom.

Protium The name given to the isotope of hydrogen with atomic mass of one.

For more than five decades, scientists have been trying to develop a method for bringing under control the awesome fusion power of a hydrogen bomb for use in commercial power plants. One of the most promising approaches appears to be a process in which two deuterons are fused to make a proton and a triton (the nucleus of a hydrogen-3 isotope). The triton and another deuteron then fuse to produce a helium nucleus, with the release of very large amounts of energy. So far, the technical details for making this process a commercially viable source of energy has not been completely worked out. However, the best approach seems to involve using a super-hot gas called plasma that is contained within a magnetic field. As of 2001, British scientists with the United Kingdom Atomic Energy Authority state that making smaller versions of previously used fusion reactors could help succeed in making the first commercial fusion reactor. Their pioneering work continues into 2007.

See also Nuclear fusion; Radioactive tracers.

Resources

BOOKS

Emsley, John. Natures Building Blocks: An A-Z Guide to the Elements. Oxford, UK: Oxford University Press, 2003.

Rioden, John S. Hydrogen: The Essential Element.Cambridge, MA: Harvard University Press, 2002.

Siekierski, Slawomir. Concise Chemistry of the Elements.Chichester, UK: Horwood Publishing, 2002.

Thomson, John F. Biological Effects of Deuterium. New York: Macmillan, 1963.

Tro, Nivaldo J. Introductory Chemistry. Upper Saddle River, NJ: Pearson Education, 2006.

David E. Newton

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Deuterium." The Gale Encyclopedia of Science. . Encyclopedia.com. 20 Nov. 2018 <https://www.encyclopedia.com>.

"Deuterium." The Gale Encyclopedia of Science. . Encyclopedia.com. (November 20, 2018). https://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/deuterium

"Deuterium." The Gale Encyclopedia of Science. . Retrieved November 20, 2018 from Encyclopedia.com: https://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/deuterium

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

Deuterium

Deuterium

Deuterium is an isotope of hydrogen with atomic mass of 2. It is represented by the symbols 2H or D. Deuterium is also known as heavy hydrogen. The nucleus of the deuterium atom, consisting of a proton and a neutron , is known as a deuteron and is represented in nuclear equations by the symbol d.


Discovery

The possible existence of an isotope of hydrogen with atomic mass of two was suspected as early as the late 1910s after Frederick Soddy had developed the concept of isotopes. Such an isotope was of particular interest to chemists. Since the hydrogen atom is the simplest of all atoms—consisting of a single proton and a single electron—it is the model for most atomic theories. An atom just slightly more complex—one that contains a single neutron—also could potentially contribute valuable information to existing atomic theories.

Among those who sought for the heavy isotope of hydrogen was Harold Urey, at the time professor of chemistry at Columbia University. Urey began his work with the realization that any isotope of hydrogen other than hydrogen-1 (also known as protium) must exist in only minute quantities. The evidence for that fact is that the atomic weight of hydrogen is only slightly more than 1.000. The fraction of any isotopes with mass greater than that value must, therefore, be very small. Urey designed an experiment, therefore, that would allow him to detect the presence of heavy hydrogen in very small concentrations.


Urey's search for deuterium

Urey's approach was to collect a large volume of liquid hydrogen and then to allow that liquid to evaporate very slowly. His hypothesis was that the lighter and more abundant protium isotope would evaporate more quickly than the heavier hydrogen-2 isotope. The volume of liquid hydrogen remaining after evaporation was nearly complete, then, would be relatively rich in the heavier isotope.

In the actual experiment, Urey allowed 4.2 qt (4 l) of liquid hydrogen to evaporate until only 0.034 oz (1 ml) remained. He then submitted that sample to analysis by spectroscopy . In spectroscopic analysis, energy is added to a sample. Atoms in the sample are excited and their electrons are raised to higher energy levels. After a moment at these higher energy levels, the electrons return to their ground state, giving off their excess energy in the form of light . The bands of light emitted in this process are characteristics for each specific kind of atom.

By analyzing the spectral pattern obtained from his 0.034 oz (1 ml) sample of liquid hydrogen, Urey was able to identify a type of atom that had never before been detected, the heavy isotope of hydrogen. The new isotope was soon assigned the name deuterium. For his discovery of the isotope, Urey was awarded the 1934 Nobel Prize in chemistry.


Properties and preparation

Deuterium is a stable isotope of hydrogen with a relative atomic mass of 2.014102 compared to the atomic mass of protium, 1.007825. Deuterium occurs to the extent of about 0.0156% in a sample of naturally occurring hydrogen. Its melting point is -426°F (-254°C)—compared to -434°F (-259°C) for protium—and its boiling point is -417°F (-249°C)–compared to -423°F (-253°C) for protium. Its macroscopic properties of color , odor, taste , and the like are the same as those for protium.

Compounds containing deuterium have slightly different properties from those containing protium. For example, the melting and boiling points of heavy water are, respectively, 38.86°F (3.81°C) and 214.56°F (101.42°C). In addition, deuterium bonds tend to be somewhat stronger than protium bonds. Thus chemical reactions involving deuterium-containing compounds tend to go more slowly than do those with protium.

Deuterium is now prepared largely by the electrolysis of heavy water, that is, water made from deuterium and oxygen (D2O). Once a great rarity, heavy water is now produced rather easily and inexpensively in very large volumes.


Uses

Deuterium has primarily two uses, as a tracer in research and in thermonuclear fusion reactions. A tracer is any atom or group of atoms whose participation in a physical, chemical, or biological reaction can be easily observed. Radioactive isotopes are perhaps the most familiar kind of tracer. They can be tracked in various types of changes because of the radiation they emit.

Deuterium is an effective tracer because of its mass. When it replaces protium in a compound, its presence can easily be detected because it weights twice as much as a protium atom. Also, as mentioned above, the bonds formed by deuterium with other atoms are slightly different from those formed by protium with other atoms. Thus, it is often possible to figure out what detailed changes take place at various stages of a chemical reaction using deuterium as a tracer.


Fusion reactions

Scientists now believe that energy produced in the sun and other stars is released as the result of a series of thermonuclear fusion reactions. The term fusion refers to the fact that two small nuclei, such as two hydrogen nuclei, fuse—or join together—to form a larger nucleus. The term thermonuclear means that such reactions normally occur only at very high temperatures, typically a few millions of degrees Celsius. Interest in fusion reactions arises not only because of their role in the manufacture of stellar energy, but also because of their potential value as sources of energy here on Earth .

Deuterium plays a critical role in most thermonuclear fusion reactions. In the solar process, for example, the fusion sequence appears to begin when two protium nuclei fuse to form a single deuteron. The deuteron is used up in later stages of the cycle by which four protium nuclei are converted to a single helium nucleus.

In the late 1940s and early 1950s scientists found a way of duplicating the process by which the sun's energy is produced in the form of thermonuclear fusion weapons, the so-called hydrogen bomb. The detonating device in this type of weapon was lithium deuteride, a compound of lithium metal and deuterium. The detonator was placed on the casing of an ordinary fission ("atomic") bomb. When the fission bomb detonated, it set off further nuclear reactions in the lithium deuteride which, in turn, set of fusion reactions in the larger hydrogen bomb.

For more than four decades, scientists have been trying to develop a method for bringing under control the awesome fusion power of a hydrogen bomb for use in commercial power plants. One of the most promising approaches appears to be a process in which two deuterons are fused to make a proton and a triton (the nucleus of a hydrogen-3 isotope). The triton and another deuteron then fuse to produce a helium nucleus, with the release of very large amounts of energy. So far, the technical details for making this process a commercially viable source of energy have not been completely worked out.

See also Nuclear fusion; Radioactive tracers.


Resources

books

Asimov, Isaac. Asimov's Biographical Encyclopedia of Science and Technology. 2nd revised edition. Garden City, NY: Doubleday & Company, Inc., 1982.

Greenwood, N.N., and A. Earnshaw. Chemistry of the Elements. 2nd ed. Oxford: Butterworth-Heinneman Press, 1997. Joesten, Melvin D., David O. Johnston, John T. Netterville, and

James L. Wood. World of Chemistry. Philadelphia: Saunders, 1991.

Thomson, John F. Biological Effects of Deuterium. New York: Macmillan, 1963.


David E. Newton

KEY TERMS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Deuteron

—A proton and a neutron; the nucleus of a deuterium atom.

Protium

—The name given to the isotope of hydrogen with atomic mass of one.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Deuterium." The Gale Encyclopedia of Science. . Encyclopedia.com. 20 Nov. 2018 <https://www.encyclopedia.com>.

"Deuterium." The Gale Encyclopedia of Science. . Encyclopedia.com. (November 20, 2018). https://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/deuterium-0

"Deuterium." The Gale Encyclopedia of Science. . Retrieved November 20, 2018 from Encyclopedia.com: https://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/deuterium-0

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.