Skip to content
Dabour HubLEARN · PRACTICE · EXPLORESign inStudent

8.4.2The Periodic Table

Oxidation and Reduction in Terms of Electrons — Cambridge IGCSE Chemistry 0620 Revision Notes & Topical Questions

5 min read 5 parts Lesson 14 of 23 Unit quiz

📚 Cambridge IGCSE Chemistry 0620 Hub / Topical Revision
🩺
100% Curriculum Specification Match Lesson Doctor Verified
The only platform with 100% curriculum specification match and verified interactive question banks.
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
0%read

Part 1 of 5Electron Definitions

Electron transfer gives the more general definition of redox reactions.

Oxidation
  • Oxidation Oxidation is the loss of electrons, so a species that loses electrons has been oxidised.
Reduction
  • Reduction Reduction is the gain of electrons, so a species that gains electrons has been reduced.
OILRIG
  • OILRIG Oxidation Is Loss, Reduction Is Gain, a simple way to remember which definition is which.
Redox
  • Redox When one species loses electrons and another gains them in the same reaction, the reaction is a redox reaction.

Part 2 of 5A Displacement Example

Iron reacting with copper(II) sulfate solution shows electron transfer clearly.

1
Iron reacts with copper(II) sulfate solution: Fe(s) + CuSO₄(aq) → FeSO₄(aq) + Cu(s).
2
Sulfate ions do not change, so they are spectator ions, leaving the ionic equation Fe(s) + Cu²⁺(aq) → Fe²⁺(aq) + Cu(s).
3
The iron atom loses two electrons to form Fe²⁺, so the iron is oxidised.
4
The copper(II) ion gains two electrons to form a copper atom, so the copper(II) ion is reduced.

Part 3 of 5Identifying the Changes

A systematic method works for any equation.

Identifying the Changes
Step one
  • Step one Write the change for each species, noting how many electrons are lost or gained.
Step two
  • Step two Label each change as oxidation (loss of electrons) or reduction (gain of electrons).
Charge clue
  • Charge clue A species whose positive charge increases has lost electrons, and one whose positive charge decreases has gained them.
Check
  • Check In Mg + Cu²⁺ → Mg²⁺ + Cu, magnesium loses two electrons and copper(II) ions gain two electrons.

Part 4 of 5Worked Example

Question Which species is reduced in the reaction Mg(s) + Cu²⁺(aq) → Mg²⁺(aq) + Cu(s)?

  1. Mg → Mg²⁺each magnesium atom loses two electrons, so magnesium is oxidised.
  2. Cu²⁺ → Cueach copper(II) ion gains two electrons, so the copper(II) ion is reduced.
  3. The species that gains electrons is the one that is reduced.

Answer The copper(II) ion, Cu²⁺, is reduced.

Part 5 of 5Exam Checklist & Tips

8.4.2 – Key Points for the Exam

  • Electron A negatively charged particle that can be lost or gained in a reaction.
  • Spectator ion An ion that is unchanged by a reaction and is left out of the ionic equation.
  • Ionic equation An equation showing only the ions and species that take part in a reaction.
  • OILRIG A memory aid meaning oxidation is loss and reduction is gain of electrons.

Common Mistakes

  • Using the wrong definitionoxidation is the loss of electrons, not the gain.
  • Naming copper as reduced when the copper(II) ion is reduced; name the species precisely.
  • Leaving spectator ions in the equation when an ionic equation is requested.
  • Confusing the loss of electrons with the loss of oxygen, which is a different definition.

Last updated:

\n