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ScienceQuest

Nitric oxide (NO) Lewis structure

11 valence electrons, linear

N O
NO as the Lewis Structure Generator draws it: lone pairs as dots, the odd electron ringed.

Build NO step by step in the Lewis Structure Generator

What is the Lewis structure of NO?

Nitric oxide, NO, has 11 valence electrons. Its two atoms are joined by one N=O double bond. It carries one lone pair on the N and two on the O. One electron is left unpaired, on the N. Every formal charge is zero. As two atoms it is linear, and the molecule is polar.

Valence electrons in NO

Element Group Valence electrons Atoms Electrons
Nitrogen 15 5 1 5
Oxygen 16 6 1 6
Total 11

In one line: 5 + 6 = 11. Each atom brings the valence electrons its group gives it.

How to draw the NO Lewis structure

  1. Count the valence electrons. Valence electrons: N 5 and O 6. 5 + 6 = 11.
  2. Join the two atoms. With only two atoms there is no choice to make: they bond to each other.
  3. Join the atoms with single bonds. One single bond uses 2 electrons, leaving 11 − 2 = 9.
  4. Complete the outer atoms. The outer O takes 6 electrons as lone pairs to reach eight, leaving 9 − 6 = 3.
  5. Put the rest on N. The 3 left go as one lone pair on N and one unpaired electron, and N now has 5 electrons round it.
  6. Make multiple bonds where needed. N has only 5 electrons, so one lone pair moves into the bond, making an N=O bond, and N now has 7, one of them unpaired.

Lone pairs and formal charges in NO

Atom Number Bonds Lone pairs Electrons round it Formal charge, V − N − B/2
N 1 one double bond 1 and 1 unpaired electron 7 5 − 3 − 2 = 0
O 1 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 0, the molecule’s overall charge.

Shape and polarity of NO

Central atom none, two atoms
Electron geometry linear
Molecular geometry linear
Ideal bond angle none, two atoms
Polarity, an estimate polar

The electronegativities differ by 0.40, so the shared electrons sit nearer O.

Notes on the NO Lewis structure

NO Lewis structure compared with its molecular orbital diagram

Lewis structure Molecular orbital diagram
Bond order 2 2.5
Unpaired electrons 1 1

In the molecular orbital diagram NO’s 11 valence electrons put 8 in bonding orbitals and 3 in antibonding ones, so its bond order is (8 − 3)/2 = 2.5. The Lewis structure gives a bond order of 2 against the diagram’s 2.5. The measured bond length is 115 pm (Huber and Herzberg, Constants of Diatomic Molecules, 1979). The Molecular Orbital Diagram Visualizer draws the diagram level by level.

Work with NO