Answer :
Final answer:
The expected Lewis structure for nitrous acid (HNO₂) would have a formal charge of 0 on both nitrogen and oxygen, which corresponds to option 3, aligning with the principle that the sum of formal charges in a neutral molecule should be zero.
Explanation:
When determining which of the following structures we would expect for nitrous acid and the formal charges on its atoms, we need to remember that the sum of the formal charges in a neutral molecule should be zero. Nitrogen normally has five valence electrons. In its stable form, it will strive to have its formal charge close to zero. Oxygen, on the other hand, will also seek to have a formal charge of zero.
The correct Lewis structure for HNO₂ would show nitrogen with a formal charge of 0, because it forms a double bond with one of the oxygen atoms and a single bond with another oxygen, which carries the OH group. The hydrogen atom connected to oxygen will not carry any formal charge, thus keeping the molecule neutral. Therefore, the structure of nitrous acid with a formal charge of 0 on nitrogen and 0 on oxygen is what we would expect (option 3).
