What are allotropes? Sketch the structure of two allotropes of carbon namely diamond and graphite. What is the impact of structure on physical properties of these two allotropes?

(N/A) The existence of an element in more than one form,having the same chemical properties but different physical properties is called allotropy. The various forms of an element are called allotropes.
Diamond has a rigid $3-D$ structure and is the hardest known substance. It is used as an abrasive and for cutting tools.
The carbon atom in diamond is $sp^3$ hybridized and forms strong covalent bonds with $4$ other carbon atoms.
Graphite is soft and slippery as it has a layered structure in which different layers are bonded to each other by weak Van der Waals forces and can slide over each other.
Hence,it is used as a lubricant.