Numford
Lewis structure

Lewis structure of NO₂⁻

18 valence electrons. One N=O double bond and one N-O single bond, with one lone pair on N. 2 resonance structures.

ONO
  • N
  • O
  • lone pair

NO₂⁻Nitrite ion

Bent

AB₂E: 2 bond pairs, 1 lone pair

  • Hybridisationsp²
  • Bond angleabout 115°
  • Polarityion, charge −1

Lewis structure

18 valence electrons, 2 resonance structures
NOO−
NOO−

Formal charges: O −1

Why this shape

  1. N has 5 valence electrons. It uses three in one double bond to O and one single bond to O, so two are left as one lone pair.
  2. Steric number = two sigma bonds + one lone pair = 3, so N is sp² hybridised. A double or triple bond counts once: only its sigma bond uses a hybrid orbital.
  3. Three electron pairs point to the corners of a flat triangle (trigonal planar electron geometry). With one lone pair in place of atoms, the atoms make a bent shape.
  4. Repulsion falls in the order lone pair to lone pair > lone pair to bond pair > bond pair to bond pair. The lone pair pushes the bond pairs closer, so the angle is about 115°, less than the ideal 120°.
  5. NO₂⁻ is an ion with an overall charge of −1, so it is not described as polar or non-polar.
Working

How to draw it

  1. Count the valence electrons: N 5 + 2 × O 6 + 1 for the ⁻ charge = 18 valence electrons, 9 pairs.
  2. Put N in the middle and join it to the two outer atoms with single bonds.
  3. Give each outer atom lone pairs until it has an octet (H needs only two electrons), then put any electrons left over on the central atom.
  4. Where an atom is still short of an octet, turn a lone pair of its neighbour into a shared pair: that makes a double or triple bond.
  5. Result: one N=O double bond and one N-O single bond, with one lone pair on N.
  6. Formal charge = valence electrons − lone pair electrons − number of bonds. Here: O −1.
  7. The double bond can sit in two equivalent ways, so there are two resonance structures. The real ion is a hybrid of them.

Class 11, Chapter 4 Chemical Bonding and Molecular Structure.

Questions

Lewis structure of NO2-: quick answers

How many valence electrons are in NO2-?

N 5 + 2 × O 6 + 1 for the ⁻ charge = 18 valence electrons, 9 pairs.

What are the formal charges in the Lewis structure of NO2-?

O −1; every other atom is zero. Formal charge = valence electrons - lone pair electrons - number of bonds.

How many resonance structures does NO2- have?

2. The double bond can sit in two equivalent ways, so there are two resonance structures. The real ion is a hybrid of them.

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