What is Allotropy?
[[File:GraphiteUSGOV.jpg|thumb|[[Graphite]] is one allotrope of [[carbon]]]] [[File:Diamond.jpg|thumb|[[Diamond]] is another allotrope of carbon]] '''Allotropy''' (or '''allotropism''') is when a [[chemical element]] can exist in two or more different forms in the same physical [[State of matter|state or phase]]. These different forms are called '''allotropes'''. Therefore, an allotrope is a different structure in which an element appears.<ref>{{GoldBookRef|title=Allotrope|file=A00243|accessdate=August 11, 2015}}</ref> This happens when the [[atoms]] of the element are [[chemical bond|bonded]] together in a different way. For example, the [[allotropes of carbon]] include: * [[diamond]], where the carbon atoms are bonded together in a [[Tetrahedron|four-cornered]] [[lattice]] arrangement; * [[graphite]], where the carbon atoms are bonded together in sheets of a [[Hexagon|six-sided]] lattice; * [[graphene]], single sheets of graphite; and * [[fullerene]]s, where the carbon atoms are bonded together in [[sphere]]s, [[cylinder]]s or [[Ellipsoid|egg-shaped]] formations Only some elements have allotropes. The term ''allotropy'' is used for elements only, not for [[chemical compound|compounds]]. The more general term, used for any crystalline material, is [[Polymorphism (materials science)|polymorphism]]. Allotropy refers only to different forms of an element within the same state (i.e., different [[solid]], [[liquid]] or [[gas]] forms); these different states are not, themselves, considered examples of allotropy. ==References== {{reflist}} {{chem-stub}} [[Category:Chemistry]] [[Category:Physical chemistry]]