How many valid resonance structures can be drawn for the carbonate ion, CO_3^{2-}?

• A. 3
• B. 4
• C. 1
• D. 2

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the structure of the carbonate ion, CO_3^{2-}. It consists of one carbon atom centrally bonded to three oxygen atoms, with an overall charge of -2.
2. Step 2: Draw the Lewis structure by placing the carbon atom in the center and connecting it to three oxygen atoms with single bonds initially. Then, add lone pairs to complete the octets of the oxygen atoms and assign the two extra electrons to account for the -2 charge.
3. Step 3: Identify that resonance structures arise from the delocalization of electrons, specifically the placement of double bonds between carbon and oxygen atoms. Since carbon can form a double bond with any one of the three oxygen atoms, each arrangement represents a valid resonance structure.
4. Step 4: Draw each resonance structure by moving the double bond to a different oxygen atom while keeping the other bonds as single bonds and adjusting the formal charges accordingly to maintain the overall -2 charge.
5. Step 5: Count the number of unique resonance structures formed by placing the double bond with each of the three oxygen atoms. This will give the total number of valid resonance structures for the carbonate ion.