Oxidation and Reduction
Oxidation loses electrons; reduction gains electrons.
About this topic
Oxidation is loss of electrons (increase in oxidation number); reduction is gain of electrons (decrease in oxidation number). They always occur together in redox reactions. The oxidising agent is reduced, accepting electrons, and the reducing agent is oxidised, giving electrons. A memory aid is OIL RIG: oxidation is loss, reduction is gain.
Oxidation numbers track electron bookkeeping: elements in their pure form are 0, simple ions equal their charge, oxygen is usually minus 2, hydrogen is plus 1 with nonmetals, and the sum equals the charge on the species. Example: Zn + Cu2+ gives Zn2+ + Cu. Zinc goes from 0 to plus 2 (oxidised) and copper from plus 2 to 0 (reduced). Half-reactions show each process separately. Many redox reactions involve oxygen, such as burning and rusting, but not all do.
Applications: batteries, corrosion, photosynthesis and respiration, bleaching, metal extraction and electroplating. In cellular respiration, glucose is oxidised and oxygen reduced, releasing energy. Bleach whitens by oxidising coloured molecules.
Common misconceptions are that oxidation always involves oxygen, which is the historical meaning; and that the oxidising agent is the species that is oxidised, when it is actually the one that is reduced. Remember that electrons cannot be created or destroyed, so the total lost equals the total gained.
Key ideas
- OIL RIG
- Oxidation numbers track electrons
- Always occur together
Quick check
Use cases: where Oxidation and Reduction helps
- Homework: review the key idea behind Oxidation and Reduction before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Oxidation and Reduction without notes.
- Visual learning: play with the interactive lab to see how Oxidation and Reduction changes when you adjust its inputs.
- Teaching a friend: explain Oxidation and Reduction in your own words, then compare your version with the key ideas.
Chemistry explains medicine, food, cleaning products, fuels and building materials.
Frequently asked questions
What is Oxidation and Reduction?
Oxidation loses electrons; reduction gains electrons.
What will I learn in Oxidation and Reduction?
OIL RIG. Oxidation numbers track electrons. Always occur together.
Is Oxidation and Reduction part of Chemistry?
Yes. It is one of 150 Chemistry topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Oxidation and Reduction lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Oxidation and Reduction?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.