Difference between revisions of "Allotropy"
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The term was first proposed by [[Jöns Jakob Berzelius]] in 1841:<ref>{{citation | last = Jensen | first = W. B. | title = The Origin of the Term Allotrope | journal = J. Chem. Educ. | year = 2006 | volume = 83 | issue = 6 | pages = 838–39 | doi = 10.1021/ed083p838}}.</ref> it is derived from the Greek {{Polytonic|άλλοτροπἱα}} (''allotropia''; variation, changeableness), from {{Polytonic|ἄλλος}} (''allos''; other, different) and {{Polytonic|τρόπος}} (''tropos''; turn of mind, manner).<ref>{{Citation | contribution = allotropy | title = A New English Dictionary on Historical Principles | volume = 1 | publisher = Oxford University Press | year = 1888 | page = 238}}.</ref> | The term was first proposed by [[Jöns Jakob Berzelius]] in 1841:<ref>{{citation | last = Jensen | first = W. B. | title = The Origin of the Term Allotrope | journal = J. Chem. Educ. | year = 2006 | volume = 83 | issue = 6 | pages = 838–39 | doi = 10.1021/ed083p838}}.</ref> it is derived from the Greek {{Polytonic|άλλοτροπἱα}} (''allotropia''; variation, changeableness), from {{Polytonic|ἄλλος}} (''allos''; other, different) and {{Polytonic|τρόπος}} (''tropos''; turn of mind, manner).<ref>{{Citation | contribution = allotropy | title = A New English Dictionary on Historical Principles | volume = 1 | publisher = Oxford University Press | year = 1888 | page = 238}}.</ref> | ||
| − | 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. Allotropy is most pronounced in groups 14, 15 and 16 of the periodic table. | + | 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.<ref>{{GoldBookRef|title=metastability (of a phase)|file=M03871|accessdate=2010-04-05}}.</ref> 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 [[phase]]s rather than allotropes. |
==Nomenclature== | ==Nomenclature== | ||
| − | Most allotropes have long-accepted [[semisystematic name]]s (e.g., [[red phosphorus]], [[white phosphorus]]) or [[trivial name]]s (e.g., [[ozone]], graphite). A systematic nomenclature is available,<ref>{{RedBook2005|pages=49–51}}.</ref> but is not widely used. | + | Most allotropes have long-accepted [[semisystematic name]]s (e.g., [[red phosphorus]], [[white phosphorus]]) or [[trivial name]]s (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,<ref>{{RedBook2005|pages=49–51}}.</ref> but is not widely used. |
==References== | ==References== | ||
Revision as of 13:52, 5 April 2010
| C graphite diamond [60]fullerene glassy carbon |
N | O dioxygen ozone |
| Si | P white phosphorus black 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 ºC 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
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See also the corresponding article on Wikipedia. |
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