Graphite is one of the most well-known examples of a conductive non-metal. Its ability to conduct electricity makes it useful in electrodes, batteries, and industrial processes. For IB Chemistry students, understanding why graphite conducts is essential in bonding, hybridization, and structure–property relationships. This article breaks down the explanation clearly and links it to concepts you need for your exams.
The Structure of Graphite
Graphite is made of carbon atoms arranged in layers.
Each carbon atom uses three of its electrons to form three sigma (σ) bonds with neighboring carbon atoms.
This creates:
- Flat hexagonal sheets
- Strong covalent bonds within the layers
- Weak forces between layers
These layers can slide over each other, giving graphite its lubricating and soft properties.
The Key Reason: Delocalized Electrons
Each carbon atom in graphite has four valence electrons, but uses only three for bonding.
The remaining one electron per carbon atom becomes delocalized.
These delocalized electrons:
- Are free to move throughout the entire layer
- Act as mobile charge carriers
- Allow electrical conductivity similar to metals
This is the fundamental reason graphite conducts electricity: it contains free-moving electrons.
Hybridization in Graphite (IB Concept)
Graphite is sp² hybridized.
This means:
- Three sp² orbitals form σ-bonds
- One unhybridized p-orbital remains
- p-orbitals overlap sideways, forming a delocalized π-electron system across the sheet
This extensive network of overlapping p-orbitals creates a π-electron cloud, enabling electrons to move freely.
Understanding hybridization is vital because it explains why graphite behaves differently from diamond, despite both being forms of carbon.
Why Diamond Does Not Conduct Electricity
Diamond is also carbon, but each atom forms four σ-bonds (sp³ hybridization).
There are no delocalized electrons, and all electrons are locked into covalent bonds.
Therefore:
- Graphite conducts
- Diamond does not
This contrast is a common exam comparison in IB Chemistry.
Electrical Conductivity Is Directional
Graphite conducts electricity within layers (called basal planes), but not between layers.
Why?
- Within layers: delocalized electrons can move easily
- Between layers: weak London dispersion forces prevent electron movement
This directional property allows graphite to be used in specific applications where controlled conductivity is important.
Applications of Graphite’s Conductivity
Graphite’s structure makes it ideal for:
- Electrodes in batteries and electrolysis
- Graphene production (single-layer graphite)
- Electrical brushes in motors
- Lubricants
- Conductive materials in electronics
Its conductivity and stability make graphite useful in high-temperature and corrosive environments.
Why Does Graphite Have Weak Interlayer Forces?
The layers in graphite are held together by weak London dispersion forces.
This allows layers to:
- Slide over each other
- Be easily separated
- Form soft, flaky materials
These weak forces are also why graphite feels slippery and why pencil lead marks paper so easily.
FAQs
Does graphite conduct better than metals?
Graphite conducts well but not as efficiently as most metals. However, its conductivity combined with heat resistance makes it useful where metals would oxidize or melt.
How is graphite different from graphene?
Graphene is a single layer of carbon atoms. It conducts even better than graphite because electrons move without interlayer interference. Graphite is simply stacked graphene layers.
Why do delocalized electrons matter so much?
Delocalized electrons are free to move, allowing electrical and thermal conductivity. Without them, materials behave as insulators.
Conclusion
Graphite conducts electricity because each carbon atom contributes a delocalized electron that can move freely through its sp²-bonded layers. This unique structure—layered hexagonal sheets, delocalized π-electrons, and weak interlayer forces—gives graphite properties that make it valuable in both industrial chemistry and IB Chemistry understanding. By mastering the structural explanation, you’ll be able to answer bonding and materials questions confidently on your exams.
