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Chemistry And Compounds

Oxygen is one of the most active of all chemical elements. The oxygen-oxygen bond in diatomic oxygen is relatively strong, but once broken, the atomic oxygen formed (O) reacts readily with the vast majority of elements. The noble gases and noble metals are the most important exceptions, although oxy compounds of most of these elements are also known and can be prepared by indirect methods.

The reaction between oxygen and another element generally results in the formation of a binary compound known as an oxide. The reaction itself is known as oxidation. For example, the oxidation reaction between oxygen and sodium produces sodium oxide. In many cases, an element may form more than one oxide. Copper, as an example, forms both copper(I) (cuprous) oxide and copper(II) (cupric) oxide. Nitrogen forms five oxides: nitrous oxide (N2O), nitric oxide (NO), dinitrogen trioxide (N2O3), nitrogen dioxide (NO2), and dinitrogen pentoxide (N2O5).

Perhaps the most important of all oxides is water, by far the most abundant compound on the planet. Water is composed of two hydrogen atoms bonded to a single oxygen atom by means of a strong covalent bond.

In many cases, the reaction between oxygen and another element is highly exothermic. One of the best known of such reactions is the one that takes place between carbon and oxygen, to form (usually) carbon dioxide and carbon monoxide. It is this reaction, which takes place when coal burns, that was responsible to a significant extent for the development of huge new energy sources during the Industrial Revolution that transformed human society.

Oxygen also reacts with a number of compounds. For example, hydrocarbons react with oxygen at high temperatures to form (primarily) carbon dioxide and water vapor. Oxidation that takes place very rapidly, usually at high temperatures, is known as combustion. The combustion of hydrocarbons in petroleum and natural gas has been another major source of energy in human civilization over the past 200 years.

Some forms of oxidation occur more slowly, without the production of noticeable heat or light. When plants and animals die, for example, the organic materials of which they are made slowly react with oxygen in the atmosphere. This form of oxidation is known as decay. The decay of organic matter is a highly complex chemical phenomenon, with a large variety of chemical products formed in the reaction.

Inorganic materials also react slowly with oxygen. When iron and certain other metals are exposed to oxygen (in the presence of water), they form oxides. The best known of all metallic oxides is probably rust, a hydrated form of iron(III) (ferric) oxide with the general formula Fe2O3 • nH2O. The rusting of bridges, buildings, motor vehicles, tools, fences, and other structures is a major economic problem throughout the world. A number of techniques, such as galvanizing, tinning, painting, and enameling are used to reduce or prevent the rusting of materials.



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Greenwood, N.N., and A. Earnshaw. Chemistry of the Elements. 2nd ed. Oxford: Butterworth-Heinemann Press, 1997.

Hawley, Gessner G. The Condensed Chemical Dictionary. New York: Van Nostrand Reinhold Company, 9th ed, 1977.

Lane, Nick. Oxygen: The Molecule That Made the World. Oxford: Oxford University Press, 2003.

Lide, D.R., ed. CRC Handbook of Chemistry and Physics Boca Raton: CRC Press, 2001.

Sawyer, Donald T. Oxygen Chemistry. New York: Oxford University Press, 1991.

Trefil, James. Encyclopedia of Science and Technology. The Reference Works, Inc., 2001.

David E. Newton



—One of two or more forms of an element.


—A form of oxidation that occurs so rapidly that noticeable heat and light are produced.


—The process by which large hydrocarbon molecules are broken down into smaller components.


—The process by which an electrical current is used to break a compound apart into its components.


—Two molecules in which the number of atoms and the types of atoms are identical, but their arrangement in space is different, resulting in different chemical and physical properties.


—The solid portion of the Earth, especially the outer crustal region.


—An abbreviation commonly used for liquid oxygen.


—The science and technology that deals with the winning of metals from their ores and their conversion into forms that have practical value.

Nascent oxygen

—An allotrope of oxygen whose molecules each contain a single oxygen atom.


—An allotrope of oxygen that consists of three atoms per molecule.

Producer gas

—A synthetic fuel that consists primarily of carbon monoxide and hydrogen gases.

Ultraviolet radiation

—Radiation similar to visible light but of shorter wavelength, and thus higher energy.

Additional topics

Science EncyclopediaScience & Philosophy: Overdamped to PeatOxygen - General Properties, Where Oxygen Comes From, How We Use Oxygen, Chemistry And Compounds