Lesson · C.3.3
Oxidation and reduction
Assign oxidation numbers, spot the oxidiser and the reducer, and read a redox equation the way the HESI A2 expects, with the rules laid out plainly.
ObjectiveC.3.3Read5 minExam weightQuantitative Chemistry ≈ 24% of Chemistry
This lesson is part of the full Study Guide
Unlock every lesson, unit, and quiz across every subject. The Chemistry quantitative chemistry unit is included.
See editions and pricing →What you will be able to do
- Assign an oxidation number to any atom in a compound or ion using the five standard rules.
- Identify which reactant is oxidised and which is reduced in a given reaction.
- Name the oxidising agent and the reducing agent in a redox pair.
What the lesson concludes
- Oxidation is loss of electrons, reduction is gain of electrons, and the two always happen together.
- OIL RIG is the whole method in one line: Oxidation Is Loss, Reduction Is Gain.
- An element's own atoms in their pure form always have an oxidation number of zero.
- The oxidising agent gets reduced and the reducing agent gets oxidised, a swap that trips up most first attempts.
- The oxidation numbers in a neutral compound sum to zero, and in a polyatomic ion they sum to the ion's charge.