Graphite

Structure of Graphite

Graphite is made up of layers of carbon atoms arranged in a hexagonal pattern. Each carbon atom forms strong covalent bonds with three other carbon atoms in the same layer, creating flat sheets of hexagonal rings. These layers are stacked on top of each other, but the forces holding the layers together are weak intermolecular forces (called van der Waals forces).

Because the layers are only weakly attracted to each other, they can slide over one another easily, which gives graphite its slippery feel.

Bonding in Graphite

Within each layer, the carbon atoms are bonded by strong covalent bonds. Each carbon atom uses three of its four outer electrons to form these bonds with neighbouring carbon atoms.

The fourth outer electron of each carbon atom is not used in bonding and becomes delocalised, meaning it is free to move throughout the layers. These delocalised electrons allow graphite to conduct electricity along the layers. This is similar to metals, where delocalised electrons also enable electrical conductivity.

Graphite also has a very high melting point because a lot of energy is needed to break the strong covalent bonds within the layers.

For instance, the strong covalent bonds in the layers require a lot of heat energy to break, so graphite melts at very high temperatures (above 36006C).

Properties of Graphite

• Graphite is soft and slippery because the layers can slide over each other easily due to weak forces between them.
• It conducts electricity because of the delocalised electrons that can move freely within the layers.
• Graphite has a high melting point due to the strong covalent bonds within the layers.

Uses of Graphite

• Lubricants: Graphite is used as a dry lubricant in machines where oils cannot be used because it reduces friction between moving parts.
• Pencils: The "lead" in pencils is actually graphite mixed with clay. The layers slide off onto the paper easily, leaving a mark.
• Electrodes: Graphite conducts electricity and is chemically inert, so it is used as electrodes in electrolysis.
• High temperature materials: Because of its high melting point, graphite is used to line furnaces and make crucibles for melting metals.

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