Write all the resonance structures of carbonate ion (CO32-)?

Difficult to draw on this site, but just draw C double bond O, and add 2 more single bond O to the carbon. On each single bond O, put 3 lone pairs electrons, and on the double bonded O put 2 lone pairs, so each O has 8 electrons. Then simply alter the position of the double bond, so that each O gets the double bond for a total of 3 resonance structures. Put brackets around all of them with a 2- charge, and you're done.

The resonance structures of carbonate ion is shown below :

https://c1.staticflickr.com/9/8752/29415300833_66e2097336_o.png