Graphite is soft because the bonding between its layers of carbon atoms is weak; thus, the layers detach easily from one another and flake off, according to the University of California Santa Barbara. Although graphite is made solely from carbon atoms like diamond, it is not hard due to the way the atoms are arranged and held together through chemical bonds.
The BBC notes that graphite is a large covalent structure made of carbon atoms. Every carbon atom is joined to three other carbon atoms, forming layers. These layers have much weaker bonds than covalent bonds, allowing the layers to slide over each other and cause the graphite to become soft. Graphite also has the ability to conduct electricity between the layers of carbon atoms.
Graphite is typically used as lead for pencils. Layers of graphite rub off when the pencil moves across the paper. Furthermore, it is used as a lubricant and also as an electrode in electrolysis.
According to the GCSE Science, the flat layers of graphite form hexagonal shapes, and they are called graphene sheets. Every layer has strong covalent bonds, although the bonds between the layers are not strong. Carbon has four electrons in the outer shell. Three electrons are used for bonding in the graphene sheet, while the fourth electron is a free electron.