Three resonance structures of the given anion are possible. One is given, but it is incomplete. Complete the given structure by adding nonbonding electrons and formal charges. Draw the two remaining resonance structures (in any order), including nonbonding electrons and formal charges. Omit curved arrows. Structure A: Complete the resonance structure. Structure B: Draw a resonance structure. Select Draw Rings More Erase Select Draw Rings More Erase C None
T he Correct Answer and Explanation is :
To provide an accurate answer, I need to know which anion or base structure you are referring to. Since you mentioned “the given anion” and “Structure A” but didn’t include an image or specify the compound (e.g., NO₃⁻, CO₃²⁻, O₃, etc.), I’ll choose a common example that fits your description and is often used in such exercises: the nitrate ion, NO₃⁻.
✅ Correct Resonance Structures for NO₃⁻ (Nitrate Ion)
Structure A (Completed)
- Nitrogen (N) is the central atom.
- One N=O double bond.
- Two N–O single bonds with each oxygen carrying a full negative charge.
- All oxygen atoms have complete octets (8 electrons).
- Nitrogen has a formal charge of +1; each singly bonded oxygen has a formal charge of –1.
Structure B (Resonance)
- Move the double bond to a different oxygen.
- Result: a different oxygen now has a double bond (N=O), and the other two have single bonds with negative charges.
- Still maintains overall –1 charge.
Structure C (Resonance)
- Shift the double bond to the third oxygen.
- Now that oxygen has a double bond; others carry the negative charges.
All three resonance structures are equivalent, with negative charge delocalized over the three oxygen atoms.
🧠 Explanation
Resonance is a concept used to represent the delocalization of electrons in molecules or ions that cannot be described adequately by a single Lewis structure. In the case of the nitrate ion (NO₃⁻), the negative charge is delocalized over three oxygen atoms, which is better represented using resonance structures.
The nitrate ion consists of a central nitrogen atom bonded to three oxygen atoms and carries a total charge of –1. Nitrogen makes three sigma bonds with the three oxygen atoms and uses one of those to form a pi bond (a double bond) with one of the oxygens. The remaining two oxygen atoms are each bonded via single bonds and carry a full negative formal charge.
The three resonance structures differ only in the position of the double bond and the location of the negative charge. Despite having different Lewis structures, they represent the same actual structure — a resonance hybrid — where all three N–O bonds are equal in length and intermediate in character (between a single and a double bond).
Each resonance structure obeys the octet rule and minimizes formal charges as much as possible. Nitrogen bears a formal charge of +1 to balance the two –1 charges from the singly bonded oxygen atoms, resulting in a net charge of –1 for the ion.
This delocalization of charge stabilizes the nitrate ion and is a key reason for its high solubility and reactivity in chemical and biological systems.
If your anion is not nitrate (NO₃⁻), please upload the structure or provide its name or formula so I can give the exact answer.
