Revision notes for AQA GCSE Chemistry Graphene and fullerenes. Open the guide for explanations and worked examples. Written against the AQA GCSE Chemistry (8462) specification, so the content matches what's examinable rather than general Chemistry background.
Graphene and fullerenes
What you'll learn
- How a single carbon sheet can be extremely strong and conduct electricity.
- How to link structure and bonding to uses in electronics and composites — materials made by combining substances to improve properties.
- What hollow carbon cages and tubes are, and how to recognise them in diagrams.
- Why carbon nanotubes are useful in nanotechnology, electronics and materials.
First, carbon bonding in one layer
Carbon has four electrons in its outer shell — the part of the atom involved in bonding. A covalent bond is a strong bond made when two atoms share a pair of electrons.
In graphite, carbon atoms are arranged in flat layers. Inside each layer, each carbon atom forms three covalent bonds to three other carbon atoms. The atoms form a repeating pattern of hexagons, a bit like a sheet of chicken wire.
Because carbon has four outer-shell electrons but only forms three covalent bonds in this layer, one electron from each carbon is free to move through the layer.
Definition
Delocalised electron
A delocalised electron is an electron that is not fixed between one pair of atoms. It can move through part of a structure and carry electrical charge.
The three shapes you need to recognise
A molecule is a fixed group of atoms joined by covalent bonds. Some carbon structures are giant sheets, while others are separate hollow molecules.
The diagram shows the key shapes in this topic: graphene is a flat sheet, Buckminsterfullerene is a hollow sphere, and a carbon nanotube is a hollow tube.
Graphene
Definition
Graphene
Graphene is a single layer of graphite: a one-atom-thick sheet of carbon atoms joined in hexagonal rings.
Graphene is sometimes described as a two-dimensional material. That does not mean it has literally no thickness — it means it is only one atom thick, so its thickness is extremely tiny compared with its length and width.
Structure of graphene
In graphene:
- each carbon atom is bonded to three other carbon atoms
- the atoms form a regular hexagonal pattern
- the covalent bonds within the sheet are very strong
- delocalised electrons can move through the sheet
Common Mistake
Counting carbon bonds in graphene
Do not say each carbon atom has four covalent bonds in graphene. Each carbon atom is bonded to three other carbon atoms; the remaining outer-shell electron is delocalised.
Properties of graphene
Graphene has useful properties because of its structure and bonding.
It is very strong because the carbon atoms are joined by many strong covalent bonds in a continuous sheet. It is also light and thin because the sheet is only one atom thick.
Graphene can conduct electricity, meaning electrical charge can move through it. This happens because its delocalised electrons can move through the sheet.
Graphene also has a very large surface area for its mass. Surface area means the amount of exposed surface. A very thin sheet exposes a lot of carbon atoms, which can be useful in sensors and composites.
Key Idea
Structure → property → use
For graphene, the main chain is: three strong covalent bonds per carbon give strength, and delocalised electrons allow electrical conduction. These properties make graphene useful in electronics and composites.
Example
Explaining graphene in a flexible electronic device
A manufacturer wants a material for a thin, flexible conducting layer. Explain why graphene is suitable.
- Graphene is one atom thick, so a layer made from it can be extremely thin and light rather than bulky.
- Each carbon atom is joined to three others by strong covalent bonds, so the sheet is strong when pulled.
- The remaining outer-shell electrons are delocalised, so charge can move through the sheet and graphene can conduct electricity.
- These properties match the use: a thin, strong conducting layer is useful in flexible electronics.
Fullerenes
Definition
Fullerene
Fullerenes are molecules of carbon atoms with hollow shapes. Their structures are based on hexagonal rings of carbon atoms, but they may also contain rings with five or seven carbon atoms.
A hexagonal ring has six atoms in the ring. A pentagonal ring has five atoms, and a heptagonal ring has seven atoms. These different ring sizes allow the carbon structure to curve and close into a hollow shape.
The first fullerene to be discovered was Buckminsterfullerene, with the formula C60\text{C}_{60}C60. It contains 60 carbon atoms and has a spherical shape, often compared with a football.
Uses of fullerenes
Fullerenes can be useful because they are tiny, hollow carbon structures.
Examples include:
- drug delivery: hollow fullerene structures can carry or attach to other molecules
- lubricants: substances that reduce friction; roughly spherical fullerenes can help surfaces slide past each other
- catalysts or catalyst supports: a catalyst speeds up a reaction without being used up, and fullerene structures can provide a useful surface
Common Mistake
Fullerene does not only mean C60
Buckminsterfullerene, C60\text{C}_{60}C60, is one example of a fullerene. Other hollow carbon molecules are also fullerenes, and carbon nanotubes count as fullerenes too.
Example
Recognising a fullerene from clues
A diagram shows a closed hollow carbon cage containing hexagons and pentagons. The label says C70\text{C}_{70}C70. Decide whether it is graphene, Buckminsterfullerene or another fullerene.
- The structure is a closed hollow cage, so it is not graphene, because graphene is an open flat sheet.
- The structure contains carbon rings and has a fixed formula, C70\text{C}_{70}C70, so it is a carbon molecule with a hollow shape: a fullerene.
- It is not Buckminsterfullerene because Buckminsterfullerene is specifically C60\text{C}_{60}C60, not C70\text{C}_{70}C70.
Carbon nanotubes
Definition
Carbon nanotube
A carbon nanotube is a cylindrical fullerene: a hollow tube made from carbon atoms arranged in a hexagonal network.
The word cylindrical means tube-shaped. Carbon nanotubes have a very high length to diameter ratio. The diameter is the distance across the tube, and the ratio compares how long the tube is with how wide it is.
Nanotubes are often discussed in nanotechnology, which means making or using structures on the nanometre scale. One nanometre is 1×10−9 m1 \times 10^{-9}\ \text{m}1×10−9 m.
Properties of carbon nanotubes
Carbon nanotubes are useful because they can be:
- very strong in tension, meaning hard to pull apart
- low density, meaning they have a small mass for their volume
- good electrical conductors, because they contain delocalised electrons
- useful at very small sizes because their diameter can be only a few nanometres
Uses of carbon nanotubes
Carbon nanotubes can be used in:
- nanotechnology, such as tiny sensors or very small-scale devices
- electronics, such as small conducting wires or components
- materials and composites, where they reinforce materials to make them stronger without adding much mass
Example
Calculating a length-to-diameter ratio
A carbon nanotube is 5000 nm long and has a diameter of 5 nm. Show why this is a high length to diameter ratio.
- Check the units first: both measurements are in nanometres, so no unit conversion is needed.
- Divide the length by the diameter: lengthdiameter=5000 nm5 nm=1000\frac{\text{length}}{\text{diameter}} = \frac{5000\ \text{nm}}{5\ \text{nm}} = 1000diameterlength=5 nm5000 nm=1000.
- Interpret the result: the nanotube is 1000 times longer than it is wide, so its length to diameter ratio is 1000:1, which is very high.
How to tell them apart in diagrams
Exam diagrams often show 3D objects on a flat page, so focus on the shape and whether the structure is open or closed.
- Graphene: one flat sheet, one atom thick, hexagonal pattern, not a closed cage.
- Fullerene: hollow carbon molecule, often a sphere or cage, with hexagons and sometimes pentagons or heptagons.
- Buckminsterfullerene: the spherical fullerene C60\text{C}_{60}C60.
- Carbon nanotube: a hollow cylinder, like a tube, with a very high length to diameter ratio.
Tip
Use the bonding chain
When explaining a property, use the chain structure/bonding → property → use. For example: delocalised electrons → conducts electricity → useful in electronics.
Exam technique
In the exam
- If asked about graphene, always link the property to bonding: strong covalent bonds explain strength; delocalised electrons explain electrical conductivity.
- For recognition questions, decide whether the carbon structure is a flat sheet, a closed hollow cage, or a tube.
- For uses, pair the material with a reason: nanotubes reinforce composites because they are strong and low density; graphene is useful in electronics because it conducts and is very thin.
Self review
Check yourself
- How does graphene’s structure explain both its strength and its electrical conductivity?
- What features would tell you a diagram shows a fullerene rather than graphene?
- Why are carbon nanotubes useful in composites and electronics?
Structure and bonding of carbon
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