NO₃ Nitrate Ion Lewis Structure: Everything You Need to Know

Understanding the Lewis structure of the nitrate ion (NO₃⁻) is essential for students of chemistry, especially when studying inorganic compounds and molecular bonding. This article breaks down the Lewis structure of NO₃⁻, explains its geometric shape, resonances, and bonding behavior, helping you master this key concept in chemical bonding.


Understanding the Context

What is NO₃⁻ (Nitrate Ion)?

The nitrate ion (NO₃⁻) is a polyatomic anion consisting of one nitrogen atom bonded to three oxygen atoms, with an extra negative charge. It commonly appears in fertilizers, water treatment, and environmental chemistry, making its structure and bonding fundamentals important for science learners.


Nitrogen Nitrate Lewis Structure: Step-by-Step

Key Insights

Step 1: Count Total Valence Electrons

  • Nitrogen (N): 5 valence electrons
  • Each oxygen (O): 6 valence electrons × 3 = 18 electrons
  • Add 1 extra electron due to the −1 charge
    Total electrons = 5 + 18 + 1 = 24 electrons

Step 2: Draw the Skeletal Structure

Place the nitrogen atom at the center, surrounded by three oxygen atoms. Nitrogen is less electronegative than oxygen but has a lone pair.

O | N — O
| O⁻

(N-bonded to three O atoms; one O carries a −1 charge.)


Final Thoughts

Step 3: Distribute Electrons to Satisfy Octet Rule

  • Bond N–O with single bonds: uses 6 electrons
  • Each oxygen has 3 lone pairs: 3 × 6 = 18 electrons
  • Remaining electrons = 24 − 6 = 18 → used for lone pairs
  • Distribute lone pairs so all atoms meet the octet rule (most favorable).

Oxygen typically has 6–8–6 electron arrangements, but here resonance requires adjustment.


Step 4: Apply Formal Charge to Optimize Structure

Formal charge helps identify the best Lewis structure.

  • Assign formal charges:
    • N: 5 − (4 + ½×2) = 5 − 5 = 0
    • Each O: 6 − (6 + ½×2) = 6 − 7 = −1
    • Total formal charge: 0 + (−1)×3 = −3 → too large

To fix this, convert one lone pair from an oxygen into a double bond using a resonance form.


Step 5: Resonance Structures of NO₃⁻