Question

What is allotropy? Give examples of allotropes.

Answer 1

In allotropism the same element is present in different forms in molecular level but varies in their physical properties. The basic atom in graphite and diamond is carbon but the arrangement of atoms are different in both the compounds.

Complete step by step answer:
The property of chemical elements to exist in two forms or more than two forms having the same physical state is known as allotropy. The elements which exist in two or more than two forms are known as allotropes. In allotropes, the atoms present in the element are joined together and arranged in different manner.
Example: The allotropes of carbon are diamond where the carbon atom is joined together in a tetrahedral lattice structure, graphite where the carbon atoms are joined together in a hexagonal lattice, graphene where the carbon atoms are joined together in a single graphite sheet and fullerenes where the carbon atoms are joined together in a spherical arrangement. The allotropes of oxygen atom are dioxygen ${O_2}$ and ozone ${O_3}$. The allotropes of phosphorus are white phosphorus which is a crystalline solid formed of tetraphosphorus molecules and red phosphorus which is an amorphous polymeric solid. The allotropes of Sulphur are rhombic Sulphur, monoclinic Sulphur and plastic Sulphur.

Note: The allotropy is only used for elements and not for chemical compounds. When the term allotropism is used for crystalline substance, then it is known as polymorphism. The term allotropy is used for different types of elements of the same atom but all present in the same phase.