How many equivalent resonance structures can be drawn for the sulfate ion, SO_4^{2-}?

• A. 4
• B. 3
• C. 2
• D. 6

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the structure of the sulfate ion, SO_4^{2-}. It consists of a sulfur atom centrally bonded to four oxygen atoms, with an overall charge of -2.
2. Step 2: Recognize that resonance structures involve different ways of placing double bonds and formal charges while keeping the same arrangement of atoms. For sulfate, the sulfur can form double bonds with oxygen atoms to satisfy the octet rule and distribute charges.
3. Step 3: Draw the Lewis structure with sulfur double bonded to one oxygen and single bonded to the other three oxygens, each single bonded oxygen carrying a negative charge. This is one resonance form.
4. Step 4: Generate other resonance structures by moving the double bond to a different oxygen atom each time, while adjusting formal charges accordingly. Each oxygen can take turns forming the double bond with sulfur.
5. Step 5: Count the total number of unique resonance structures created by placing the double bond with each of the four oxygen atoms. This gives the number of equivalent resonance structures for SO_4^{2-}.