This article is about isomorphism in chemistry. For other types of isomorphism, see Isomorphism (disambiguation).
In chemistry, isomorphism has meanings both at the level of crystallography and at a molecular level. In crystallography, crystals are isomorphous if they have identical symmetry and if the atomic positions can be described with a set of parameters (unit cell dimensions and fractional coordinates) whose numerical values differ only slightly.[1]
Forsterite
Molecules are isomorphous if they have similar shapes. The coordination complexestris(acetylacetonato)iron (Fe(acac)3) and tris(acetylacetonato)aluminium (Al(acac)3) are isomorphous. These compounds, both of D3 symmetry have very similar shapes, as determined by bond lengths and bond angles. Isomorphous compounds give rise to isomorphous crystals and form solid solutions.[2] Historically, crystal shape was defined by measuring the angles between crystal faces with a goniometer. Whereas crystals of Fe(acac)3 are deep red and crystals of Al(acac)3 are colorless, a solid solution of the two, i.e. Fe1−xAlx(acac)3 will be deep or pale pink depending on the Fe/Al ratio, x.
Double sulfates, such as Tutton's salt, with the generic formula MI2MII(SO4)2.6H2O, where MI is an alkali metal and MII is a divalent ion of Mg, Mn, Fe, Co, Ni, Cu or Zn, form a series of isomorphous compounds which were important in the nineteenth century in establishing the correct atomic weights of the transition elements. Alums, such as KAl(SO4)2.12H2O, are another series of isomorphous compounds, though there are three series of alums with similar external structures, but slightly different internal structures. Many spinels are also isomorphous.
In order to form isomorphous crystals two substances must have the same chemical formulation (i.e., atoms in the same ratio), they must contain atoms which have corresponding chemical properties and the sizes of corresponding atoms should be similar. These requirements ensure that the forces within and between molecules and ions are approximately similar and result in crystals that have the same internal structure. Even though the space group is the same, the unit cell dimensions will be slightly different because of the different sizes of the atoms involved.
Mitscherlich's lawedit
Mitscherlich's law of isomorphism, or the law of isomorphism, is an approximatelaw suggesting that crystals composed of the same number of similar elements tend to demonstrate isomorphism.[3]
Mitscherlich's law is named for German chemist Eilhard Mitscherlich,[4] who formulated the law and published it between 1819 and 1823.[5]
According to Ferenc Szabadváry, one of the clues that helped Berzelius determine the atomic weights of the elements was "the discovery of Mitscherlich that compounds which contain the same number of atoms and have similar structures, exhibit similar crystal forms (isomorphism)."[6]
^Girolami, Gregory (2015). X-Ray Crystallography. University Science Books. ISBN978-1-891389-77-1.
^Wells, A.F. (1984). Structural Inorganic Chemistry (5th ed.). Oxford University Press. ISBN0-19-855370-6. pp 186–186 in 3rd. edition
^"Mitscherlich, Eilhard". Complete Dictionary of Scientific Biography. Encyclopedia.com. 2008.
^Schutt Hans-Werner. (1997.) Eilhard Mitscherlich: Prince of Prussian Chemistry, Chemical Heritage Foundation. ISBN9780841233454.
^Bernadette Bensaude-Vincent. (1996.) A History of Chemistry, Harvard University Press, p. 122. ISBN9780674396593.
^Szabadváry, Ferenc; Svehla, trans., Gyula (1992). History of Analytical Chemistry. Yverdon, Switzerland: Gordon and Breach Science Publishers. p. 141. ISBN978-2881245695. Retrieved 12 March 2020.
May 03, 2024
isomorphism, crystallography, this, article, about, isomorphism, chemistry, other, types, isomorphism, isomorphism, disambiguation, chemistry, isomorphism, meanings, both, level, crystallography, molecular, level, crystallography, crystals, isomorphous, they, . This article is about isomorphism in chemistry For other types of isomorphism see Isomorphism disambiguation In chemistry isomorphism has meanings both at the level of crystallography and at a molecular level In crystallography crystals are isomorphous if they have identical symmetry and if the atomic positions can be described with a set of parameters unit cell dimensions and fractional coordinates whose numerical values differ only slightly 1 Forsterite Molecules are isomorphous if they have similar shapes The coordination complexes tris acetylacetonato iron Fe acac 3 and tris acetylacetonato aluminium Al acac 3 are isomorphous These compounds both of D3 symmetry have very similar shapes as determined by bond lengths and bond angles Isomorphous compounds give rise to isomorphous crystals and form solid solutions 2 Historically crystal shape was defined by measuring the angles between crystal faces with a goniometer Whereas crystals of Fe acac 3 are deep red and crystals of Al acac 3 are colorless a solid solution of the two i e Fe1 xAlx acac 3 will be deep or pale pink depending on the Fe Al ratio x Double sulfates such as Tutton s salt with the generic formula MI2MII SO4 2 6H2O where MI is an alkali metal and MII is a divalent ion of Mg Mn Fe Co Ni Cu or Zn form a series of isomorphous compounds which were important in the nineteenth century in establishing the correct atomic weights of the transition elements Alums such as KAl SO4 2 12H2O are another series of isomorphous compounds though there are three series of alums with similar external structures but slightly different internal structures Many spinels are also isomorphous In order to form isomorphous crystals two substances must have the same chemical formulation i e atoms in the same ratio they must contain atoms which have corresponding chemical properties and the sizes of corresponding atoms should be similar These requirements ensure that the forces within and between molecules and ions are approximately similar and result in crystals that have the same internal structure Even though the space group is the same the unit cell dimensions will be slightly different because of the different sizes of the atoms involved Mitscherlich s law editMitscherlich s law of isomorphism or the law of isomorphism is an approximate law suggesting that crystals composed of the same number of similar elements tend to demonstrate isomorphism 3 Mitscherlich s law is named for German chemist Eilhard Mitscherlich 4 who formulated the law and published it between 1819 and 1823 5 According to Ferenc Szabadvary one of the clues that helped Berzelius determine the atomic weights of the elements was the discovery of Mitscherlich that compounds which contain the same number of atoms and have similar structures exhibit similar crystal forms isomorphism 6 See also editAsterism gemology Polymorphism materials science Goldschmidt tolerance factor Solid solution Vegard s lawReferences edit Girolami Gregory 2015 X Ray Crystallography University Science Books ISBN 978 1 891389 77 1 Wells A F 1984 Structural Inorganic Chemistry 5th ed Oxford University Press ISBN 0 19 855370 6 pp 186 186 in 3rd edition Mitscherlich Eilhard Complete Dictionary of Scientific Biography Encyclopedia com 2008 Schutt Hans Werner 1997 Eilhard Mitscherlich Prince of Prussian Chemistry Chemical Heritage Foundation ISBN 9780841233454 Bernadette Bensaude Vincent 1996 A History of Chemistry Harvard University Press p 122 ISBN 9780674396593 Szabadvary Ferenc Svehla trans Gyula 1992 History of Analytical Chemistry Yverdon Switzerland Gordon and Breach Science Publishers p 141 ISBN 978 2881245695 Retrieved 12 March 2020 Retrieved from https en wikipedia org w index php title Isomorphism crystallography amp oldid 1214722409 Mitscherlich s law, wikipedia, wiki, book, books, library,
