Two or more forms of the same elements in same physical state which differ in their physical properties but have same chemical properties are called allotropic forms or (allotropes) and the phenomenon is called allotropy.
Carbon, phosphorus and sulphur are some elements which exhibit allotropy.
(i) Diamond and graphite are allotropic forms of carbon
(ii) Red phosphorus and white phosphorus are allotropes of phosphorus.
(iii) Rhombic sulphur, monoclinic sulphur and plastic sulphur are allotropic forms of sulphur.
