Differences between the properties of metals and non-metals
3 marks · NormalGraphite is a form of carbon, a non-metal. Unlike most non-metals, graphite conducts electricity. Explain why graphite is an exception among non-metals in terms of electrical conductivity.
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Graphite conducts electricity because it has delocalised electrons that are free to move. These delocalised electrons allow electrical charge to flow through the layers of carbon atoms.
Also accept: Graphite conducts electricity because each carbon atom forms three bonds, leaving one electron free to move in the structure.
Common mistakes: Stating graphite conducts because it is a metal; Omitting description of delocalised electrons or mobile charge carriers
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Marking points
M1 · 1 mark · Refers to the presence of delocalised electrons in graphite.
B1 · 1 mark · States these delocalised electrons can move freely.
B2 · 1 mark · Links delocalised electrons to the ability of graphite to conduct electricity.
Worked solution
Graphite is a form of carbon where each atom forms three covalent bonds, leaving one electron per atom delocalised. These delocalised electrons are free to move throughout the layers. Because these electrons can move, graphite can conduct electricity, unlike most non-metals.