Many reactions are classified as oxidation-reduction or “redox” reactions. The only specific characteristic that makes a reaction a redox reaction is that there must be a transfer of electrons, causing a change in the oxidation states of the elements involved. So, how do you know what elements or compounds are oxidized and which are reduced? The key to identifying a reaction as a redox reaction is to look for changes in the oxidation numbers. Remember, in oxidation, there is a loss of electrons. In reduction there is a gain of electrons. Here is a hint that will allow you to remember the difference between oxidation and reduction. LEO stands for “loss of electrons is oxidation.” GER stands for “gain of electrons is reduction.” And, what does LEO the Lion say? GER.

To tell which elements have been oxidized and reduced, you need to write a balanced net-ionic equation and then half-reactions for oxidation and reduction. The half-reactions will show you both the oxidizing agent and reducing agent in the reaction. View this presentation to learn more about redox equations and discover what is oxidized and what is reduced.

View a printable version of the interactivity.

Oxidation/Reduction Reactions Review

Now that you have learned about redox reactions, complete this non-graded activity to check your knowledge. Read each question and select the appropriate answer. Then, click SUBMIT to check your response. Click on the interactivity thumbnail, and then click NEXT to get started.