Isostructural

{{Short description|Compounds having similar chemical structure}} '''Isostructural''' chemical compounds have similar chemical structures. "Isomorphous" when used in the relation to crystal structures is not synonymous: in addition to the same atomic connectivity that characterises isostructural compounds, isomorphous substances crystallise in the same space group and have the same unit cell dimensions.<ref>{{cite book |last=Wells |first=A. F. |title=Structural Inorganic Chemistry |edition=3rd |year=1970 |publisher=Clarendon Press |location=Oxford |isbn=0-19-855125-8 |page=182}}</ref> The IUCR definition<ref>[http://reference.iucr.org/dictionary/Isostructural_crystals "Isostructural crystals"], IUCR Online Dictionary of CRYSTALLOGRAPHY.</ref> used by crystallographers is: {{blockquote|Two crystals are said to be isostructural, if they have the same structure, but not necessarily the same cell dimensions nor the same chemical composition, and with a "comparable" variability in the atomic coordinates to that of the cell dimensions and chemical composition. For instance, calcite CaCO₃, sodium nitrate NaNO₃ and iron borate FeBO₃ are isostructural. One also speaks of isostructural series, or of isostructural polymorphs or isostructural phase transitions. The term isotypic is synonymous with isostructural.}}

Examples include: * I-Gold(I) bromide is isostructural with gold(I) chloride * Borazine is isostructural with benzene * Indium(I) bromide is isostructural with β-thallium(I) iodide and has a distorted rock salt structure.

Many minerals are isostructural when they differ only in the nature of a cation.

Compounds which are isoelectronic usually have similar chemical structures. For example, methane, CH₄, and the ammonium ion, NH₄⁺, are isoelectric and are isostructural as both have a tetrahedral structure. The C–H and N–H bond lengths are different and crystal structures are completely different because the ammonium ion only occurs in salts.

== References == {{reflist}}

Category:Crystallography Category:Molecular geometry

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