What is Allotropy

 If the change in structure is reversible then the polymorphism is called as 'allotropy'.Allotropy (Gr. allos, other, and tropos, manner) is a behavior exhibited by certain chemical elements: these elements can exist in two or more dissimilar forms, known as allotropes of that element. In every allotrope, the element's atoms are bonded together in a dissimilar manner. Allotropes are dissimilar structural modifications of an element.

The phenomenon of allotropy is sometimes also known as allotropism.