Resonance

1. Resonance By Amber DeKoeyer And Kelli Dhuy

2. What it is • There are, in practice, “half-bonds” when only one double bond is needed but there is nothing to make it double bond with one atom vs. another • Only happens in covalent compounds

3. For example… • Look at ozone • There’s no reason for the double bond to form with the left O instead of the one on the right • Actually, each O has a “half bond,” their behavior and size are half-way between that of a single and that of a double bond

4. How do I Show Resonance? • Remember how to draw Lewis Dot Diagrams? • Add up valence electrons • Distribute them so every atom (with the exception of H and He) has a full octet, forming single, double, and triple bonds as needed • Dots represent electrons and lines represent bonds, whole bonds • These rules don’t allow for “half bonds,” so…

5. …to show resonance… …draw all the possibilities with double arrows in between to show that you are “averaging” them.

6. What About Covalent Ions? • Covalent Ions can also show resonance, just add brackets • Remember to show all the possibilities • For example, look at this drawing of

7. Benzene: A Resonance Shortcut

8. Works Cited Brown and LeMay, Chemistry: The Central Science Pearson Education, Inc. Upper Saddle River, New Jersey 01458, 2003