page_title: Allotropy
hierarchical_section_title: Allotropy
caption_attribution_description: Diamond and graphite samples with their respective structures. The bottom right formation of carbon is what is known as "graphene," characterized by infinite, single atom sheets of carbon.
context_page_description: Allotropy or allotropism is the property of some chemical elements to exist in two or more different forms, in the same physical state, known as allotropes of the elements. Allotropes are different structural modifications of an element; the atoms of the element are bonded together in a different manner. For example, the allotropes of carbon include diamond, graphite, graphene, and fullerenes. The term allotropy is used for elements only, not for compounds. The more general term, used for any crystalline material, is polymorphism. Allotropy refers only to different forms of an element within the same phase; the differences between these states would not alone constitute examples of allotropy.
  For some elements, allotropes have different molecular formulae despite difference in phase; for example, two allotropes of oxygen can both exist in the solid, liquid and gaseous states. Other elements do not maintain distinct allotropes in different phases; for example, phosphorus has numerous solid allotropes, which all revert to the same P₄ form when melted to the liquid state.
context_section_description: Allotropy or allotropism (from Ancient Greek  ἄλλος (allos), meaning 'other', and  τρόπος (tropos), meaning 'manner, form') is the property of some chemical elements to exist in two or more different forms, in the same physical state, known as allotropes of the elements. Allotropes are different structural modifications of an element; the atoms of the element are bonded together in a different manner. For example, the allotropes of carbon include diamond (the carbon atoms are bonded together in a tetrahedral lattice arrangement), graphite (the carbon atoms are bonded together in sheets of a hexagonal lattice), graphene (single sheets of graphite), and fullerenes (the carbon atoms are bonded together in spherical, tubular, or ellipsoidal formations). The term allotropy is used for elements only, not for compounds. The more general term, used for any crystalline material, is polymorphism. Allotropy refers only to different forms of an element within the same phase (i.e.:  solid, liquid or gas states); the differences between these states would not alone constitute examples of allotropy.
  For some elements, allotropes have different molecular formulae despite difference in phase; for example, two allotropes of oxygen (dioxygen, O₂, and ozone, O₃) can both exist in the solid, liquid and gaseous states. Other elements do not maintain distinct allotropes in different phases; for example, phosphorus has numerous solid allotropes, which all revert to the same P₄ form when melted to the liquid state.
caption: Diamond and graphite are two allotropes of carbon: pure forms of the same element that differ in crystalline structure.
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