How many significant resonance structures are needed to describe the structure of HNO3 (nitric acid)?

• A. 1
• B. 4
• C. 3
• D. 2

Answer: (C)

Verified step by step guidance

1. Step 1: Understand that resonance structures are different Lewis structures for the same molecule that differ only in the placement of electrons, not atoms.
2. Step 2: Draw the Lewis structure of HNO\_3, noting that the nitrogen atom is bonded to one hydroxyl group (OH) and two oxygen atoms, with one of the oxygens typically double bonded to nitrogen.
3. Step 3: Identify possible resonance structures by moving the double bond between nitrogen and oxygen to different oxygen atoms, while keeping the overall connectivity the same.
4. Step 4: Count all valid resonance structures where the octet rule is satisfied for all atoms and formal charges are minimized.
5. Step 5: Conclude that the number of significant resonance structures corresponds to the different ways the double bond and charges can be distributed among the oxygen atoms, which is three for HNO\_3.