Overview
This lecture introduces redox (reduction-oxidation) reactions, focusing on electron transfer, key definitions, and the basics of identifying oxidation, reduction, and associated agents.
Ionic Bonding and Redox Basics
- Ionic bonding involves the transfer of electrons between a metal and a non-metal, forming ions with opposite charges.
- Redox reactions are defined by the transfer of electrons between substances.
- Redox is different from acid-base reactions, which involve the transfer of protons (H⁺ ions).
Key Concepts: Oxidation and Reduction
- Oxidation is the loss of electrons by a substance.
- Reduction is the gain of electrons by a substance.
- The mnemonic "OIL RIG" helps: Oxidation Is Loss, Reduction Is Gain (of electrons).
- Oxidation and reduction occur simultaneously in redox reactions.
Oxidation Numbers and Agents
- Oxidation number increases when a substance is oxidized and decreases when reduced.
- An oxidizing agent is reduced (it gains electrons).
- A reducing agent is oxidized (it loses electrons).
- Sodium and potassium lose electrons (oxidized, reducing agents); chlorine gains electrons (reduced, oxidizing agent).
Examples and Half Reactions
- Sodium (Na) loses an electron to chlorine (Cl), becoming Na⁺ (oxidized); Cl becomes Cl⁻ (reduced).
- In half-reactions:
- Oxidation half-reaction has electrons on the product side (right).
- Reduction half-reaction has electrons on the reactant side (left).
- When balancing and writing half-reactions, always use a single arrow.
Using Redox Tables
- Redox tables list half-reactions and can be read in both directions.
- In exams, write half-reactions with a single arrow, not a double arrow.
- The direction of electron flow in half-reactions identifies oxidation or reduction.
Key Terms & Definitions
- Redox Reaction — a reaction involving the transfer of electrons.
- Oxidation — loss of electrons (increase in oxidation number).
- Reduction — gain of electrons (decrease in oxidation number).
- Oxidizing Agent — substance that is reduced (gains electrons).
- Reducing Agent — substance that is oxidized (loses electrons).
- Oxidation Number — a value representing the electron loss or gain for an atom.
Action Items / Next Steps
- Watch videos on oxidation numbers, using redox tables, and writing/balancing half-reactions.
- Review rules for determining oxidation numbers.
- Practice identifying oxidation, reduction, and agents in sample reactions.