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Edexcel International A Level Chemistry

Topic 8A
Redox Chemistry

Redox chemistry gives you a way of following electrons through a reaction. These pages build the oxidation number rules, then use them to define oxidation and reduction, to write and combine half-equations, to recognise disproportionation and to classify unfamiliar reactions.

Exam Unit
Unit 2
WCH12/01 – IAS
Specification Points
8.1 – 8.10
10 points covered
Sub-topics
4 lessons
Revision notes available
Exam Board
Edexcel IAL
Pearson International

Revision Notes

4 revision notes, in the order the specification teaches them.

A ball climbing a staircase of oxidation steps
1

Oxidation Numbers

Oxidation numbers: the rules, calculating them in compounds, ions, peroxides and metal hydrides, Roman numerals and writing formulae.

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Electrons moving from one particle to another
2

Electron Transfer and Half-Equations

Redox as electron transfer: oxidising and reducing agents, oxidation number changes, writing ionic half-equations and combining them into full ionic equations.

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One particle splitting into a higher and a lower state
3

Disproportionation

Disproportionation: recognising it with oxidation numbers, chlorine in water and alkali, hydrogen peroxide, copper(I) and which species cannot disproportionate.

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One atom shrinking as its partner grows
4

Redox Classification

Classifying reactions with oxidation numbers: redox or not, s-block and p-block examples, metals with acids, and unfamiliar equations.

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Summary Map

Download, print and revise the key facts of this topic at a glance.

Summary map

Download, print and revise the key facts of this topic at a glance.

Illustration of a summary map: compounds joined by reaction arrows
Summary map · PDF

Redox Map

Edexcel International A Level Chemistry · Unit 2 · Topic 8A Redox Chemistry

The whole topic on one A4 page: oxidation number rules, Roman numerals, half-equations, disproportionation and a table of polyatomic ions with their charges.

Download the map6 key ideas + 16 ions · A4 portrait · print ready

© 2026 Online Learning System. For personal study: printing is allowed; editing, copying and redistribution are not.

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Study Cards

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Specification

Every specification point in this topic, in the exam board's own words. Rate how confident you are with each one.

Official Pearson Edexcel IAL documentsSpecification (opens the Pearson Edexcel IAL website in a new tab)Data booklet (opens the Pearson Edexcel IAL website in a new tab)

Self-assessment · 26 points

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8.1

  1. a

    know what is meant by the term 'oxidation number'

    Revise
  2. b

    understand the rules for assigning oxidation numbers

    Revise

8.2

  1. a

    be able to calculate oxidation numbers of elements in compounds

    Revise
  2. b

    be able to calculate oxidation numbers of elements in ions

    Revise
  3. c

    be able to calculate oxidation numbers of elements in peroxides

    Revise
  4. d

    be able to calculate oxidation numbers of elements in metal hydrides

    Revise

8.3

  1. 8.3

    be able to indicate the oxidation number of an element in a compound or an ion, using a Roman numeral

    Revise

8.4

  1. 8.4

    be able to write formulae given oxidation numbers

    Revise

8.5

  1. a

    understand oxidation in terms of electron transfer

    Revise
  2. b

    understand reduction in terms of electron transfer

    Revise
  3. c

    understand oxidation in terms of changes in oxidation number

    Revise
  4. d

    understand reduction in terms of changes in oxidation number

    Revise
  5. e

    apply oxidation and reduction ideas to reactions of s-block elements

    Revise
  6. f

    apply oxidation and reduction ideas to reactions of p-block elements

    Revise

8.6

  1. a

    know that oxidising agents gain electrons

    Revise
  2. b

    know that reducing agents lose electrons

    Revise

8.7

  1. a

    understand that a disproportionation reaction involves an element in a single species being oxidised

    Revise
  2. b

    understand that a disproportionation reaction involves an element in a single species being reduced simultaneously

    Revise

8.8

  1. a

    know that oxidation number is useful for classifying reactions as redox

    Revise
  2. b

    know that oxidation number is useful for classifying reactions as disproportionation

    Revise

8.9

  1. a i

    understand that metals generally form positive ions by loss of electrons

    Revise
  2. a ii

    understand that formation of metal positive ions involves an increase in oxidation number

    Revise
  3. b i

    understand that non-metals generally form negative ions by gain of electrons

    Revise
  4. b ii

    understand that formation of non-metal negative ions involves a decrease in oxidation number

    Revise

8.10

  1. a

    be able to write ionic half-equations

    Revise
  2. b

    be able to use ionic half-equations to construct full ionic equations

    Revise