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Dinitrogen tetroxide (N₂O₄) Lewis structure

34 valence electrons, trigonal planar

N N O O O O + + − −
N₂O₄ as the Lewis Structure Generator draws it: lone pairs as dots, nonzero formal charges circled.

Build N₂O₄ step by step in the Lewis Structure Generator

What is the Lewis structure of N₂O₄?

Dinitrogen tetroxide, N₂O₄, has 34 valence electrons. The two N atoms bond to each other, and the molecule has two N=O double bonds, one N−N single bond and two N−O single bonds. Its formal charges are +1 on each central N and −1 on each single-bonded O. It has four equivalent resonance forms. Each N is AX₃: trigonal planar.

Valence electrons in N₂O₄

Element Group Valence electrons Atoms Electrons
Nitrogen 15 5 2 10
Oxygen 16 6 4 24
Total 34

In one line: 2 × 5 + 4 × 6 = 34. Each atom brings the valence electrons its group gives it.

How to draw the N₂O₄ Lewis structure

  1. Count the valence electrons. Valence electrons: each N 5 and each O 6. 2 × 5 + 4 × 6 = 34.
  2. Bond the two central atoms. N appears twice, so the two N atoms bond to each other and share the O atoms evenly between them.
  3. Join the atoms with single bonds. Five single bonds use 10 electrons, leaving 34 − 10 = 24.
  4. Complete the outer atoms. Each outer atom takes enough lone pairs to reach eight: 4 O × 6 = 24, leaving 24 − 24 = 0.
  5. Put the rest on the central atom. Nothing is left, so each N gets no lone pair, and each N now has 6 electrons round it.
  6. Make multiple bonds where needed. Each N has only 6 electrons, so two lone pairs move into the bonds, making two N=O bonds, and both N now have 8.

Lone pairs and formal charges in N₂O₄

Atom Number Bonds Lone pairs Electrons round it Formal charge, V − N − B/2
N (central) 2 one double bond and two single bonds 0 8 5 − 0 − 4 = +1
O 2 one double bond 2 8 6 − 4 − 2 = 0
O 2 one single bond 3 8 6 − 6 − 1 = −1

V is the atom’s valence electrons, N its nonbonding electrons and B its bonding electrons. The formal charges add up to 0, the molecule’s overall charge.

Resonance structures of N₂O₄

The four forms differ only in where the electrons sit, so the real molecule is one structure, their average, the resonance hybrid. Four N−O bonds each have an average order of 3/2. Four O atoms share a formal charge of −2 between them, −1/2 each.

N N O O O O + + − −
Form 1
N N O O O O + + − −
Form 2
N N O O O O + + − −
Form 3
N N O O O O + + − −
Form 4
N N O O O O + + −1/2 −1/2 −1/2 −1/2
Resonance hybrid, partial bonds dashed

Shape and polarity of N₂O₄

Central atoms each N
VSEPR class AX₃
Electron geometry trigonal planar
Molecular geometry trigonal planar
Ideal bond angle 120°
Polarity, an estimate nonpolar

The two halves are identical and point opposite ways, so their bond dipoles cancel.

Each N has three σ bonds and no lone pairs, three electron domains in all, so its electron geometry is trigonal planar. With no lone pairs, the molecular geometry is the same.

The VSEPR Molecular Geometry viewer turns the AX₃ shape in 3D, lone pairs included.

Work with N₂O₄