The electrical conductivity of graphite is due to electrons that are:

• A. Localized in bonds
• B. Delocalized and mobile in the layers
• C. Absent
• D. Replaced by protons

Answer: (B)

Graphite conducts electricity because the carbon atoms in each layer form a network of delocalized electrons that are free to move within the layer. Each carbon uses sp2 hybrid orbitals to make three in-plane covalent bonds, leaving one electron in a p orbital that overlaps with neighboring carbons to create a continuous π-system across the layer. These delocalized electrons act as mobile charge carriers, so an electric field can drive them and produce current along the layers. The layers are held together by weaker forces, so conductivity is much better within a layer than between layers. This is why the conductivity is due to electrons that are delocalized and mobile in the layers. Localized electrons in bonds wouldn’t allow easy movement, while electrons being absent or protons replacing them wouldn’t explain the observed conductivity.