The phenomenon of occurrence of same elements in different physical forms is known as [[1]]

Allotropy is the phenomenon of the existence of the same elements in different forms having different properties. Allotropes of an element may have similar chemical properties but they differ in physical properties. The arrangements of atoms will be different in allotropes. For example diamond, graphite and fullerene are allotropes of carbon. Diamond is one of the hardest substances on earth while graphite is very soft. The occurrence of various crystalline forms of an element is the same phenomenon known as polymorphism in the context of compounds. Allotropes can be either monotropic, where one form is the most stable under all circumstances, or enantiotropic, where multiple forms are stable under various circumstances and change from one to the other in a reversible manner under specific pressures and temperatures.