Allotropy

Allotropy or allotropism is a behavior exhibited by certain chemical elements: these elements can exist in two or more different forms, known as allotropes of that element. In each allotrope, the element's atoms are bonded together in a different manner. Allotropes are different structural modifications of an element. Allotropes should not be confused with isomers, which are chemical compounds that share the same molecular formula but have different structural formulae. For example, carbon has 3 common allotropes: diamond, where the carbon atoms are bonded together in a tetrahedral lattice arrangement, graphite, where the carbon atoms are bonded together in sheets of a hexagonal lattice, and fullerenes, where the carbon atoms are bonded together in spherical, tubular, or ellipsoidal formations. Allotropy refers only to different forms of an element within the same phase or state of matter (i.e. different solid, liquid or gas forms); the changes of state between solid, liquid and gas in themselves are not considered allotropy.