Chemical Bonding: CO₃^2- Lewis Structure

Drawing the Lewis Structure for CO₃^2-

• CO₃^2- is an anion (a negative ion) seen frequently in chemistry.
• In the CO₃^2- Lewis structure carbon is the least electronnegative element. Therefore it is put in the center of the dot structure.
• For the CO₃^2- Lewis structure there are a total of 24 valence electrons available.

Transcript: Let's do the CO3 2- Lewis structure: the carbonate ion. Carbon has 4 valence electrons; Oxygen has six, we have 3 Oxygens, and this negative 2 means we have an extra two valence electrons. Add that all up: 4 plus 18 plus 2: 24 valence electrons. Carbon is the least electronegative, put that at the center. Three Oxygens go around the Carbon. We'll put two electrons between the atoms to form chemical bonds. We've used six. And then around the Oxygens: 8, 10, and 24. So we've used all 24 valence electrons. All have octets, 8 valence electrons.

The Carbon, however, only has 6 valence electrons. Let's move two valence electrons from here to form a double bond with the Carbon. So this Oxygen still has 8 valence electrons but now the Carbon has 8 valence electrons. We're still using only 24 valence electrons. So the formal charges do make sense here because the black Oxygens here and here both have a formal charge of negative 1 and the Carbon and the other Oxygen are 0. So -1 plus -1, that does match up with what we have for the carbonate ion here. Because of that, this is the best Lewis structure for CO3 2-.

There's one last thing we need to do: because the CO3 2- ion has a charge of negative 2, we need to put brackets around our Lewis structure and put that negative 2 outside so everyone knows that it is an ion and it has a negative 2 charge.

That's it: that's the Lewis structure for CO3 2-. This is Dr. B., and thanks for watching.