Let's take two valence electrons here from this Oxygen and share them to form a double bond with the Carbon. Learn this topic by watchingResonance Structures Concept Videos From- http://en.wikipedia.org/wiki/Acet ate-Chemists abbreviate acetate as OAc− and AcO−. Using Formal Charge to Predict Molecular Structure. So If you start out with the acetate ion with the first carbon bonded to the second carbon, which is double bonded to an O and single bonded to an O, you'll see you have a lone pair on the O that can form a bond with carbon 2. So we had 12, 14, and 24 valence electrons. Chemistry Q&A Library Draw the Lewis structure (including resonance structures) for the acetate ion (CH3COO-). We will have to draw the Lewis Structure of CH 3 CO 2-first. The acetate ion ( Example 3.12 ) exhibits resonance. //-->.