Study GuideChemistry–Oxidation‐Reduction Reactions1.Introduction to Oxidation–Reduction (Redox) ReactionsOxidation–reduction reactions, often calledredox reactions, are among the most important types ofchemical reactions you will study. They play a key role in many real-life processes—from producingenergy in factories to releasing energy inside your own body during respiration.1.1What Happens in a Redox Reaction?At the heart of every redox reaction is thetransfer of electrons. One substance gives up electrons,and another substance receives them.•The substance thatloses electronsis said to beoxidized.•The substance thatgains electronsis said to bereduced.Even though these terms come from older chemistry ideas, they are still widely used today. Animportant point to remember is this:oxidation and reduction always happen together. You cannothave one without the other because electrons lost by one substance must be gained by another.1.2Understanding Oxidation NumbersTo keep track of which elements are oxidized and which are reduced, chemists useoxidationnumbers. An oxidation number is a value assigned to an element in a compound or reaction thatshows how many electrons it has effectively lost or gained.Here’s how oxidation numbers help us:•If an element’s oxidation numberincreases(becomes more positive), that element isoxidized.•If an element’s oxidation numberdecreases, that element isreduced.By comparing oxidation numbers before and after a reaction, we can clearly identify which substancesare oxidized and which are reduced.Preview Mode
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