Difference between revisions of "Oxygen"
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Oxygen (ˈɒksɨdʒɨn) is a colourless gas which makes up about one fifth of the Earth's atmosphere. Its name comes from the Greek ὀξύς (oxys; acid, literally "sharp", from the taste of acids) and -γενής (-genēs; producer, literally "begetter").
Contents
History
The discovery of oxygen is often credited to English chemist Joseph Priestley, although the full story is somewhat more involved. That there is a component of air which is necessary for combustion and respiration was recognized by Leonardo da Vinci in the fifteenth century, and confirmed by English chemist John Mayow in the mid-seventeenth century. However, the interpretation of these results was hampered by the rise of phlogiston theory, which stated that substances gave off phlogiston during combustion: air that was no longer capable of supporting combustion was said to be saturated with phlogiston. The unequivocal identification of oxygen as a chemical substance would have to wait for its preparation by chemical means.
The preparation was first carried out by Swedish chemist Carl Scheele on several occasions during the period 1771–73. Scheele heated various compounds such as KNO3, Mg(NO3)2 and HgO and found that they gave off a gas that he named "vitriol air", which supported combustion better than normal air.[7] Scheele's results, however, were not published until 1777. In the meantime, Priestley had isolated the gas given off by heating HgO and named it "dephlogistonated air", and published his results in 1775 after proving that the gas was different from nitrous oxide.
Priestley's work certainly had the greater impact, as he was able to discuss it with French chemist Antoine Lavoisier in October 1774 during a visit to Paris with his mentor and employer the Earl of Shelbourne.
Occurance and production
Oxygen is almost ubiquitous at the surface of the Earth. The approximate mass fractions of oxygen are: crustal rocks 46%; the human body 61%; sea water 86%. The amount fraction of oxygen in the Earth's atmosphere (at sea level) is 21.0%, amounting to some 1015 tonnes. Apart from the atmosphere, the vast majority of this oxygen is chemically combined in a wide variety of inorganic and organic compounds: in the atmosphere, oxygen exists almost entirely as dioxygen (O2) molecules, its normal elemental state, with a small (but very important) amount of ozone (O3).
While it is difficult to obtain precise statistics, oxygen is believed to be the third most important bulk industrial chemical, after sulfuric acid and lime but ahead of ammonia and nitrogen, with production of at least 100 million tonnes per year.
Allotropes
Chemical properties
Use
Physical properties
Safety
Notes and references
Notes
References
- ↑ 1.0 1.1 Oxygen. In NIST Chemistry WebBook; National Institute for Standards and Technology, <http://webbook.nist.gov/cgi/inchi/InChI%3D1S/O2/c1-2>. (accessed 15 March 2010).
- ↑ Oxygen. In Gas Encyclopedia; Air Liquide, <http://encyclopedia.airliquide.com/encyclopedia.asp?GasID=48>. (accessed 3 April 2010).
- ↑ Allred, A. L. Electronegativity values from thermochemical data. J. Inorg. Nucl. Chem. 1961, 17 (3–4), 215–21. DOI: 10.1016/0022-1902(61)80142-5.
- ↑ 4.0 4.1 Oxygen, atomic. In NIST Chemistry WebBook; National Institute for Standards and Technology, <http://webbook.nist.gov/cgi/inchi/InChI%3D1S/O>. (accessed 15 March 2010).
- ↑ Mohr, Peter J.; Taylor, Barry N. CODATA recommended values of the fundamental physical constants: 2002. Rev. Mod. Phys. 2005, 77 (1), 1–107. DOI: 10.1103/RevModPhys.77.1.
- ↑ Cox, J. D.; Wagman, D. D.; Medvedev, V. A. CODATA Key Values for Thermodynamics; Hemisphere: New York, 1989. ISBN 0891167587, <http://www.codata.org/resources/databases/key1.html>.
- ↑ Greenwood, Norman N.; Earnshaw, A. Chemistry of the Elements; Pergamon: Oxford, 1984; pp 698–756. ISBN 0-08-022057-6.
External links
See also the corresponding article on Wikipedia. |
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