Here it says determine the remaining resonance structures possible for the carbonate ion, which is CO3-2. So here we have our carbonate ion, we have our pie, our double bond on the oxygen on the top. Realize here that the oxygens that are single bonded have formal charges equal to -1, so they're depicted that way and we'd have to remember to carry over those formal charges of -1 for any other oxygens that are single bonded.

So remember in resonance we're just moving around the electrons from the Pi bonds. So way another resonance structure I could show is what if it's not the top oxygen that's double bonded, but it's the one on the left? Then we notice here that the double bonded oxygen has 2 lone pairs. So here's 2 lone pairs, and the single bonded oxygens have 3 lone pairs. Remember the single bonded oxygens have formal charges of -1 and here we put it in brackets because it has a charge.

But remember they're connected with double bonds. But who says that the oxygen on the left side is double bonded? What if it's the oxygen on the right side that's double bonded? The ones that are single bonded remember, have 3 lone pairs. The one that's double bonded has two. Remember, the single bonded oxygens each have a formal charge of -1. Put it in brackets with a charge on the outside.

And remember, these double sided arrows are what connects these resonance structures to one another. So just remember we're just showing different places the Python could have been within each of these structures. Each of them represents A resonance structure for the carbonate ion.