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Nitronium ion (NO₂⁺) Lewis structure

16 valence electrons, linear, a charge of +1

N O O + +
NO₂⁺ as the Lewis Structure Generator draws it: lone pairs as dots, nonzero formal charges circled.

Build NO₂⁺ step by step in the Lewis Structure Generator

What is the Lewis structure of NO₂⁺?

Nitronium ion, NO₂⁺, has 16 valence electrons. Nitrogen is the central atom, joined by two N=O double bonds. It carries two lone pairs on each O. Its only formal charge is +1, on the central N. N is AX₂: linear, with an ideal bond angle of 180°.

Valence electrons in NO₂⁺

Element Group Valence electrons Atoms Electrons
Nitrogen 15 5 1 5
Oxygen 16 6 2 12
Charge of 1+ −1
Total 16

In one line: 5 + 2 × 6 − 1 = 16. Each atom brings the valence electrons its group gives it, and the positive charge takes one away for each unit.

How to draw the NO₂⁺ Lewis structure

  1. Count the valence electrons. Valence electrons: N 5 and each O 6, and the 1+ charge takes 1 away. 5 + 2 × 6 − 1 = 16.
  2. Choose the central atom. N goes in the middle: N is the least electronegative atom other than H, χ 3.04 against 3.44 for O. Checked the other way, O in the middle would need an O−O bond, and electronegative atoms of one element avoid bonding to each other when they can.
  3. Join the atoms with single bonds. Two single bonds use 4 electrons, leaving 16 − 4 = 12.
  4. Complete the outer atoms. Each outer atom takes enough lone pairs to reach eight: 2 O × 6 = 12, leaving 12 − 12 = 0.
  5. Put the rest on the central atom. Nothing is left, so N gets no lone pair, and N now has 4 electrons round it.
  6. Make multiple bonds where needed. N has only 4 electrons, so two lone pairs move into the bonds, making two N=O bonds, and N now has 8.

Lone pairs and formal charges in NO₂⁺

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

V is the atom’s valence electrons, N its nonbonding electrons and B its bonding electrons. The formal charges add up to +1, the charge on the ion.

Minor resonance contributors to NO₂⁺

Ranked by the same rules, the next best arrangements are valid Lewis structures that count for less in the real ion. One that can be drawn either way round is shown once.

N O O + − + +
+1 on the central N, +1 on the triple-bonded O and −1 on the single-bonded O. Its formal charges add up to more: 3 against 1.

Shape and polarity of NO₂⁺

Central atom N
VSEPR class AX₂
Electron geometry linear
Molecular geometry linear
Ideal bond angle 180°
Polarity, an estimate not applicable

An ion carries a net charge, so whether its bond dipoles cancel is not the question polarity asks.

N has two σ bonds and no lone pairs, two electron domains in all, so its electron geometry is linear. With no lone pairs, the molecular geometry is the same.

The VSEPR Molecular Geometry viewer turns the AX₂ shape in 3D, lone pairs included.

Work with NO₂⁺