What is Allotropy? Explain the different types Crystalline forms of Carbon

Allotropy

• Allotropy is a property by which an element can exist in more than one form that is physically different and chemically similar.
• The different forms of that element are called its allotropes.
• The main reason for the existence of allotropes of an element is its method of formation or preparation.
• Carbon exists in different allotropic forms and based on its physical nature they are classified as below.

Crystalline forms of Carbon

Diamond:

• In diamond, each carbon atom shares its four valence electrons with four other carbon atoms forming four covalent bonds.
• Here the atoms are arranged in a repeated tetrahedral fashion which leads to a three-dimensional structure accounting for its hardness and rigidity.

Graphite:

• In graphite, each carbon atom is bonded to three other carbon atoms through covalent bonds in the same plane.
• This arrangement forms hexagonal layers which are held together one over the other by weak Vander Waals forces.
• Since the layers are held by weak forces, graphite is softer than diamond.

Fullerene:

• The third crystalline allotrope of carbon is fullerene.
• The best-known fullerene is Buckminster fullerene, which consists of 60 carbon atoms joined together in a series of 5 and 6-membered to form spherical molecule resembling a soccer ball. So its formula is C₆₀
• This allotrope was named as Buckminster fullerene after the American architect
• Buckminster fuller. Because its structure reminded the framework of dome shaped halls designed by Fuller for large international exhibitions, it is called by the pet name Bucky Ball.
• A large family of fullerenes exists, starting at C₂₀, and reaching up to C ₅₄₀