AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
Graphite: In graphite, one electron from each carbon atom is delocalised.
In graphite each carbon atom forms three covalent bonds, using three of its four outer electrons.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 2 of 4
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
In graphite each carbon atom forms three covalent bonds, using three of its four outer electrons. The remaining outer electron from each carbon atom becomes delocalised. These delocalised electrons are free to move throughout each layer of hexagonal rings, so graphite conducts electricity. The layers themselves are held together by weak intermolecular forces, allowing them to slide. This is why graphite is used for electrodes in electrolysis and in batteries. For example, a graphite rod conducts electricity because the delocalised electrons can carry charge through the structure. The number of delocalised electrons is one per carbon atom, so the ratio of carbon atoms to delocalised electrons is 1:1.
What earns the marks
- States that one electron from each carbon atom is delocalised in graphite.
- Explains that three of the four outer electrons per carbon atom are used in covalent bonding.
- Links delocalised electrons to the ability of graphite to conduct electricity.
- States that delocalised electrons are free to move within the layers.
- Uses the 1:1 ratio of carbon atoms to delocalised electrons correctly.
Common mistakes and how to put them right
Saying all four electrons per carbon atom are delocalised.
Put it right by stating only one electron per carbon atom is delocalised.
Saying graphite conducts because ions move.
Put it right by stating delocalised electrons carry charge.
Saying the delocalised electrons are localised between two atoms.
Put it right by stating they are free to move throughout the layer.
Exam tips
- State the number of delocalised electrons per carbon atom explicitly.
- Link delocalised electrons directly to electrical conductivity in graphite.
- Use the phrase free to move when describing delocalised electrons.
Try the lesson
The start of the Graphite: In graphite, one electron from each carbon atom is delocalised. lesson, made from checked teaching notes for this specification point.
Have a go first
In graphite, what happens to one electron from each carbon atom?
Listen
In graphite each carbon atom forms three covalent bonds, using three of its four outer electrons. The remaining outer electron from each carbon atom becomes delocalised. These delocalised electrons are free to move throughout each layer of hexagonal rings, so graphite conducts electricity. The layers themselves are held together by weak intermolecular forces, allowing them to slide. This is why graphite is used for electrodes in electrolysis and in batteries. For example, a graphite rod conducts electricity because the delocalised electrons can carry charge through the structure. The number of delocalised electrons is one per carbon atom, so the ratio of carbon atoms to delocalised electrons is 1:1. A strong answer earns marks for these points. States that one electron from each carbon atom is delocalised in graphite. Explains that three of the four outer electrons per carbon atom are used in covalent bonding. Links delocalised electrons to the ability of graphite to conduct electricity. States that delocalised electrons are free to move within the layers. A common slip: Saying all four electrons per carbon atom are delocalised. Instead, stating only one electron per carbon atom is delocalised. Exam tip: State the number of delocalised electrons per carbon atom explicitly.
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Key words
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Delocalised electrons
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Electrical conductivity
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Covalent bonding
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See every definition
- Delocalised electrons
- One electron from each carbon atom in graphite, which is free to move throughout each layer of hexagonal rings.
- Electrical conductivity
- Graphite conducts electricity because the delocalised electrons are free to move and can carry charge through the structure.
- Covalent bonding
- Each carbon atom in graphite forms three covalent bonds, using three of its four outer electrons.
Label the diagram
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1Box 1
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3Box 3
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