Difference between revisions of "Allotropy"
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| <big>'''Si'''</big> | | <big>'''Si'''</big> | ||
− | | <big>'''P'''<br/>[[black phosphorus]] | + | | <big>'''P'''</big><br/>[[black phosphorus]]<br/>[[white phosphorus]]<br/>''[[red phosphorus]]'' |
| <big>'''S'''</big><br/>[[α-sulfur]]<br/>[[β-sulfur]]<br/>[[γ-sulfur]]<br/>[[ε-sulfur]] | | <big>'''S'''</big><br/>[[α-sulfur]]<br/>[[β-sulfur]]<br/>[[γ-sulfur]]<br/>[[ε-sulfur]] | ||
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Revision as of 15:00, 5 April 2010
C graphite diamond [60]fullerene glassy carbon |
N | O dioxygen ozone |
Si | P black phosphorus white phosphorus red phosphorus |
S α-sulfur β-sulfur γ-sulfur ε-sulfur |
Ge | As α-arsenic yellow arsenic ε-arsenic amorphous arsenic |
Se α-selenium β-selenium γ-selenium grey selenium red selenium black selenium |
Sn white tin grey tin |
Sb α-antimony antimony-I antimony-II |
Te |
Pb | Bi α-bismuth ζ-bismuth |
Po α-polonium β-polonium |
Some allotropes of the elements of groups 14, 15 and 16. The most stable allotrope at 25 °C and 1 bar is listed first; amorphous allotropes are listed in italics. |
Allotropy is a phenomenon in chemistry whereby a given chemical element can exist in several different structural forms.[1] Each of these forms is called an allotrope. The best known example is that of diamond and graphite, which are both allotropes of carbon. Allotropy can be seen as a special case of polymorphism.
The term was first proposed by Jöns Jakob Berzelius in 1841:[2] it is derived from the Greek άλλοτροπἱα (allotropia; variation, changeableness), from ἄλλος (allos; other, different) and τρόπος (tropos; turn of mind, manner).[3]
At any given temperature and pressure, one allotrope will be more thermodynamically stable than the others. Nevertheless, other allotropes can exhibit substantial kinetic stability, e.g. diamond: such allotropes are said to be metastable.[4] Allotropy is most pronounced in groups 14, 15 and 16 of the periodic table. Boron also forms several allotropes: the different structural forms of the d- and f-block metals are usually referred to as phases rather than allotropes.
Nomenclature
Most allotropes have long-accepted semisystematic names (e.g., red phosphorus, white phosphorus) or trivial names (e.g., ozone, graphite). The different allotropes may also be labelled with Greek letters (e.g., α-sulfur, β-sulfur), where the α-allotrope is usually (but not always) the most stable under ambient conditions. A systematic nomenclature is available,[5] but is not widely used.
References
- ↑ allotropes, <http://goldbook.iupac.org/A00243.html> (accessed 5 April 2010), Compendium of Chemical Terminology Internet edition; International Union of Pure and Applied Chemistry (IUPAC).
- ↑ Jensen, W. B. The Origin of the Term Allotrope. J. Chem. Educ. 2006, 83 (6), 838–39. DOI: 10.1021/ed083p838.
- ↑ allotropy. In A New English Dictionary on Historical Principles; Oxford University Press, 1888; Vol. 1, p 238.
- ↑ metastability (of a phase), <http://goldbook.iupac.org/M03871.html> (accessed 5 April 2010), Compendium of Chemical Terminology Internet edition; International Union of Pure and Applied Chemistry (IUPAC).
- ↑ Nomenclature of Inorganic Chemistry; IUPAC Recommendations 2005; Royal Society of Chemistry: Cambridge, 2005; pp 49–51. ISBN 0-85404-438-8, <http://www.iupac.org/publications/books/rbook/Red_Book_2005.pdf>.
External links
See also the corresponding article on Wikipedia. |
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