Structure of Carbon Allotrope(Graphite)

When an element exists in multiple forms and one of its forms has the same chemical properties but different physical properties, then that form is called the element’s allotrope. Graphite is one of the allotropes of carbon forming a carbon allotrope structure. 

Graphite is soft and slippery because of its layered structure in which different layers are bonded by weak Van Der Waals force, which can slide over one another. Due to this reason, it can be used as a component of many lubricants, eg, it is used as a component of bicycle chain oil. 

Graphite has a high melting point because each carbon atom is bonded with three strong covalent bonds. It is also a good conductor of electricity, which makes it suitable to be used as a material for electrodes during electrolysis.

Types of graphite

• Natural graphite

It is a compound composed of minerals and naturally occurring graphitic carbon. With a stability range of temperature around 3650 degrees celsius, it is one of the best conductors of heat and electricity.

• Vein graphite

It occurs in fissures or fractures, appearing as a massive outbreak. It originates from crude oil due to extensive heat and temperature, and it gets converted into graphite. The purity level is around 70 per cent. It is used in making high friction applications such as car brakes.

• Synthetic graphite

Synthetic graphites are less crystalline than natural ones and are made of coke and pith.

There are two types of synthetic graphites:-

• The first one is pure carbon formed by blasting coal tar pitch and calcined petroleum in an electric furnace.
• The second one is produced by extensively heating calcinated petroleum pitch at around 2800-degree celsius.

Structure of graphite 

Graphite has a layered structure consisting of hexagonal rings, where each carbon atom forms three bonds with a 120-degree C-C-C bond angle, leaving the fourth one spared and is sp2 hybridised. A weak Van der Waals force of attraction holds graphite’s layers together. 

Since the force, which holds the layers together, is weak, the layers can slip over one another. The graphite layers are separated from each other by a distance of 3.40 A. The bond length of the carbon-carbon bond is 1.41 A. It is black in colour and opaque with a relative density of 2.3.

Type of bonding in graphite

Graphite has a two-dimensional planar structure. Each carbon in it is sp2  hybridised. Each individual carbon atom is bonded to three of its neighbouring carbon atoms through covalent bonds forming hexagonal planer rings in a single layer. Each atom’s last free valence electron is free to move between different layers.

Strong covalent bonds, existing between carbon atoms, require a huge amount of energy input to break. It is arranged in different hexagonal layers. However, only weak intermolecular forces exist between the different graphite layers. This explains why graphite is used in pencils. 

Not much energy is required to break the bonds between different graphite layers as it slides past each other with ease. Graphite stands out only because of its trait of conducting electricity. A carbon in graphite is bonded to 3 others (it can bind to up to four because of its valence), which means free electrons can run throughout the structure. As electricity is defined as the flow of electrons, hence, this property of graphite is what makes it a good conductor.

Applications of graphite bonding: 

1. It is used in sensors 
2. It is used in thermal management
3. It is used in batteries

These all applications require bonding graphite to a host of materials.

Usage of graphite

1. Refractories: Due to its high tolerance to heat and unchangeability, it is a widely used refractory material.  Graphite is used in the manufacturing industry as well as it helps in the production of glass and steel.
2. Nuclear reactors: Graphite absorbs fast-moving neutrons. Therefore, it is used in reactors to stabilise nuclear reactions.
3. Graphene sheets: Graphite can be used to make graphene sheets, which are nearly 100-times stronger than steel. These graphene sheets are used in making lightweight and strong sports equipment. These sheets have been used in the aerospace industry as well.

Conclusion 

Allotropes of carbon are the different forms of carbon that have similar chemical but different physical properties. Carbon has many allotropes because it has four valence electrons in its outermost shell which bonds with other carbon atoms to reach an inert state. There are two types of allotropes of carbon– Crystalline allotropes and amorphous allotrope. In this article, you have gained knowledge about graphite, one of the crystalline carbon allotrope structures, and its importance. We have also discussed the structure of graphite, bonding in graphite, its properties, types, and different uses in industry and day to day life.