Answer: Option (3) is the correct answer.
Explanation:
When an element exists in two or more different physical forms then they are known as allotropes.
For example, diamond and graphite are both allotropes of carbon.
In graphite, carbon atoms are joined together in sheets of six sided lattice. Whereas in diamond, carbon atoms are joined together in four cornered lattice.
Therefore, as these allotropes are made up of same element so they have similar chemical properties but different physical properties like melting point, boiling point etc.
Also, both of them have different molecular structure.
Thus, we can conclude that the statement the differ in their molecular structure and properties correctly describes diamond and graphite.
