2.3.2 Graphite

In this lesson, we will explore the structure and properties of graphite, a unique form of carbon. We will examine how the arrangement of carbon atoms in graphite's layered structure and the presence of delocalised electrons contribute to its properties.

Structure of Graphite

Graphite is composed of carbon atoms arranged in layers of hexagonal rings. Each carbon atom forms three covalent bonds with three neighbouring carbon atoms within a layer, resulting in a flat, two-dimensional sheet. These layers are stacked on top of each other, with weak van der Waals forces acting between the layers. Unlike in diamond, there are no covalent bonds between the layers of graphite.

Delocalised Electrons

In graphite, one electron from each carbon atom remains unutilised in the covalent bonds, resulting in delocalised electrons within the structure. These delocalised electrons are not confined to specific carbon atoms or layers but are free to move throughout the entire graphite structure. The presence of these delocalised electrons gives graphite some metal-like properties.

Properties of Graphite

• Lubricating and Slippery: The layered structure of graphite allows the layers to slide over one another with ease. This property makes graphite an effective lubricant, reducing friction between moving parts.
• Electrical Conductivity: Similar to metals, graphite is a good conductor of electricity. The presence of delocalised electrons allows for the movement of electrical charge through the layers of graphite. This makes graphite useful in various electrical and electronic applications.
• High Melting Point: The strong covalent bonds within each layer of graphite contribute to its high melting point. However, the weak van der Waals forces between the layers result in a relatively lower melting point compared to diamond.
• Soft and Brittle: Although graphite is made up of layers of covalently bonded carbon atoms, the weak forces between the layers make graphite relatively soft and brittle. This is in contrast to the exceptional hardness of diamond.

Conclusion

The properties of graphite can be explained by its unique structure and bonding. The layers of hexagonal rings, with three covalent bonds per carbon atom, give graphite its layered structure and slippery nature. The presence of delocalised electrons allows graphite to exhibit electrical conductivity, similar to metals.