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GCSE Chemistry · key term
The smallest section of a polymer chain that repeats along the chain.
Used by AQA, Edexcel and OCR
Specification 4.7.3.1 · Paper 2
The smallest group of atoms that repeats along a polymer chain.
Revise: Addition PolymerisationEach repeat unit in the polymer contains the same atoms as its monomer, although the bonds between the carbon atoms have changed.
Specification 9.20C · Paper 2
The smallest section of a polymer chain that repeats; it is shown in square brackets with continuation bonds and an outside.
When drawing a repeat unit, change C=C to C–C but keep every atom and side group attached to the same carbon.
Check every carbon has four bonds after drawing the monomer or repeat unit.
Keep each side group attached to the same carbon when changing between a monomer and its repeat unit.
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The repeat unit is the smallest section that reproduces the pattern of the chain. It is drawn inside square brackets.
Specification C6.2g · Paper 2 (Foundation), Paper 4 (Higher)
The section of a polymer chain that repeats along the chain.
Revise: Deducing Polymer StructuresThis two-carbon section is the repeat unit of poly(ethene).
Paper 1 (Foundation), Paper 2 (Foundation), Paper 3 (Higher), Paper 4 (Higher)
Revise: Addition polymer structureThen draw the repeat unit in square brackets, with a bond extending through each side to show that the chain continues. The small n outside the brackets means that the unit repeats many times; it is not part of the unit’s formula.