Q8. Assign formal charges to all atoms in the following resonance form for HNO3:

Background

Topic: Formal Charge and Resonance Structures

This question tests your understanding of how to assign formal charges to atoms in a molecule, specifically in a resonance structure. Formal charge helps chemists determine the most stable resonance form and predict reactivity.

Key Terms and Formulas

• Formal Charge (FC): The charge assigned to an atom in a molecule, assuming equal sharing of electrons in bonds.

• Formula for Formal Charge:

• Valence electrons: Number of electrons in the neutral atom (from the periodic table).

• Nonbonding electrons: Lone pairs on the atom.

• Bonding electrons: Electrons shared in bonds (count all, then divide by 2).

Step-by-Step Guidance

1. Identify the number of valence electrons for each atom: H (1), O (6), N (5).

2. For each atom (H, O(a), O(b), N, O(c)), count the number of nonbonding electrons (lone pairs) and bonding electrons (shared in bonds).

3. Apply the formal charge formula to each atom. For example, for O(a):

4. Repeat the calculation for N and each O atom (O(a), O(b), O(c)), making sure to use the correct number of lone pairs and bonds for each.

5. Compare the calculated formal charges to the answer choices to determine which matches the structure.

Try solving on your own before revealing the answer!