Editing Allotropy (section)

==History==
The concept of allotropy was originally proposed in 1840 by the Swedish scientist Baron [[Jöns Jakob Berzelius]] (1779–1848).<ref>See:
*  {{cite book |last1=Berzelius |first1=Jac. |title=Årsberättelse om Framstegen i Fysik och Kemi afgifven den 31 Mars 1840. Första delen. |trans-title=Annual Report on Progress in Physics and Chemistry submitted March 31, 1840. First part. |date=1841 |publisher=P.A. Norstedt & Söner |location=Stockholm, Sweden |page=14 |url=https://babel.hathitrust.org/cgi/pt?id=nyp.33433009789326&view=1up&seq=176 |language=Swedish}}  From p. 14:  ''"Om det ock passar väl för att uttrycka förhållandet emellan myrsyrad ethyloxid och ättiksyrad methyloxid, så är det icke passande för de olika tillstånd hos de enkla kropparne, hvari dessa blifva af skiljaktiga egenskaper, och torde för dem böra ersättas af en bättre vald benämning, t. ex. ''Allotropi'' (af ''αλλότροπος'', som betyder:  af olika beskaffenhet) eller ''allotropiskt tillstånd''."''  (If it [i.e., the word ''isomer''] is also well suited to express the relation between formic acid ethyl oxide [i.e., ethyl formate] and acetic acid methyloxide [i.e., methyl acetate], then it [i.e., the word ''isomers''] is not suitable for different conditions of simple substances, where these [substances] transform to have different properties, and [therefore the word ''isomers''] should be replaced, in their case, by a better chosen name; for example, ''Allotropy'' (from ''αλλότροπος'', which means: of different nature) or ''allotropic condition''.)
*  Republished in German:  {{cite journal |last1=Berzelius |first1=Jacob |last2=Wöhler |first2=F. |title=Jahres-Bericht über die Fortschritte der physischen Wissenschaften |journal=Jahres Bericht Über die Fortschritte der Physischen Wissenschaften |trans-title= Annual Report on Progress of the Physical Sciences |date=1841 |publisher=Laupp'schen Buchhandlung |location=Tübingen, (Germany) |volume= 20 |page=13 |url=https://babel.hathitrust.org/cgi/pt?id=umn.31951d000120766&view=1up&seq=189 |language=German}}  From p. 13:  ''"Wenn es sich auch noch gut eignet, um das Verhältniss zwischen ameisensaurem Äthyloxyd und essigsaurem Methyloxyd auszudrücken, so ist es nicht passend für ungleiche Zustände bei Körpern, in welchen diese verschiedene Eigenschaften annehmen, und dürfte für diese durch eine besser gewählte Benennung zu ersetzen sein, z. B. durch ''Allotropie'' (von ''αλλότροπος'', welches bedeutet:  von ungleicher Beschaffenheit), oder durch ''allotropischen Zustand''."'' (Even if it [i.e., the word ''isomer''] is still well suited to express the relation between ethyl formate and methyl acetate, then it is not appropriate for the distinct conditions in the case of substances where these [substances] assume different properties, and for these, [the word ''isomer''] may be replaced with a better chosen designation, e.g., with ''Allotropy'' (from ''αλλότροπος'', which means: of distinct character), or with ''allotropic condition''.)
*  Merriam-Webster online dictionary:  [https://www.merriam-webster.com/dictionary/allotropy Allotropy]</ref><ref name=Jensen>{{citation | last = Jensen | first = W. B. |author1-link=William B. Jensen | title = The Origin of the Term Allotrope | journal = J. Chem. Educ. | year = 2006 | volume = 83 | issue = 6 | pages = 838–39 | doi = 10.1021/ed083p838|bibcode = 2006JChEd..83..838J }}.</ref> The term is derived {{ety|gre|''άλλοτροπἱα'' (allotropia)|variability, changeableness}}.<ref>{{Citation | contribution = allotropy | title = A New English Dictionary on Historical Principles | volume = 1 | publisher = Oxford University Press | year = 1888 | page = 238}}.</ref> After the acceptance of [[Avogadro's law|Avogadro's hypothesis]] in 1860, it was understood that elements could exist as polyatomic molecules, and two allotropes of oxygen were recognized as O<sub>2</sub> and O<sub>3</sub>.<ref name=Jensen/> In the early 20th century, it was recognized that other cases such as carbon were due to differences in crystal structure.

By 1912, [[Wilhelm Ostwald|Ostwald]] noted that the allotropy of elements is just a special case of the phenomenon of [[Polymorphism (materials science)|polymorphism]] known for compounds, and proposed that the terms allotrope and allotropy be abandoned and replaced by polymorph and polymorphism.<ref>{{cite book |last1=Ostwald |first1=Wilhelm |last2=Taylor |first2=W.W. |title=Outlines of General Chemistry |date=1912 |publisher=Macmillan and Co., Ltd. |location=London, England |page=104 |edition=3rd |url=https://books.google.com/books?id=1w1DAAAAIAAJ&pg=PA104}}  From p. 104:  "Substances are known which exist not only in two, but even in three, four or five different solid forms; no limitation to the number is known to exist.  Such substances are called polymorphous.  The name allotropy is commonly employed in the same connexion, especially when the substance is an element.  There is no real reason for making this distinction, and it is preferable to allow the second less common name to die out."</ref><ref name=Jensen/> Although many other chemists have repeated this advice, [[IUPAC]] and most chemistry texts still favour the usage of allotrope and allotropy for elements only.<ref>Jensen 2006, citing Addison, W. E. The Allotropy of the Elements (Elsevier 1964) that many have repeated this advice.</ref>