Question

Explain the following.

Diamond, graphite and fullerenes are crystalline forms of carbon.

Answer 1

• Carbon exhibits a property of allotropy in which an element exists in more than one form in nature. 
• The chemical properties of these different forms are the same but their physical properties are different. 
• Carbon exists in crystalline as well as non-crystalline (amorphous form). 
• Crystalline form has a regular and definite arrangement of atoms. They have high melting points and boiling points.
• A crystalline form has a definite geometrical shape, sharp edges and plane surfaces. 
• Carbon has three crystalline allotropes such as diamond, graphite and fullerene.
• In the structure of diamond, every carbon atom is bonded to four neighbouring atoms by covalent bonds.
• Therefore, diamond has a tetragonal three dimensional structure which makes it very hard. 
• Brilliant and pure diamond is the hardest natural substance.
• In the structure of graphite, every carbon atom in graphite is bonded to three other carbon atoms in such a way that a hexagonal layered structure is formed. 
• A graphite crystal is made of many sheets or layers of carbon atoms. These layers slip over each other on applying pressure. One layer of graphite is called graphene. 
• Fullerene is rarely found in nature. It is found in soot and in interstellar space. 
• The first example of fullerene is Buckminster fullerene (C₆₀).
• This allotrope of carbon is named fullerene after the architect.
• Richard Buckminster Fuller because the structure of C₆₀ resembles the structure of the geodesic dome he designed.
• Molecules of fullerenes are found in the form of buckyballs and buckytubes.
• There are 30 to 900 carbon atoms in one molecule of a fullerene. C₆₀ , C₇₀ ,C₇₆ ,C₈₂ and C₈₆ are other examples of fullerene. Their molecules occur in small numbers in soot.