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ScienceQuest

Carbon dioxide (CO₂) Lewis structure

16 valence electrons, linear

C O O
CO₂ as the Lewis Structure Generator draws it: lone pairs as dots.

Build CO₂ step by step in the Lewis Structure Generator

What is the Lewis structure of CO₂?

Carbon dioxide, CO₂, has 16 valence electrons. Carbon is the central atom, joined by two C=O double bonds. It carries two lone pairs on each O. Every formal charge is zero. C is AX₂: linear, with an ideal bond angle of 180°, and the molecule is nonpolar.

Valence electrons in CO₂

Element Group Valence electrons Atoms Electrons
Carbon 14 4 1 4
Oxygen 16 6 2 12
Total 16

In one line: 4 + 2 × 6 = 16. Each atom brings the valence electrons its group gives it.

How to draw the CO₂ Lewis structure

  1. Count the valence electrons. Valence electrons: C 4 and each O 6. 4 + 2 × 6 = 16.
  2. Choose the central atom. C goes in the middle: C is the least electronegative atom other than H, χ 2.55 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 C gets no lone pair, and C now has 4 electrons round it.
  6. Make multiple bonds where needed. C has only 4 electrons, so two lone pairs move into the bonds, making two C=O bonds, and C now has 8.

Lone pairs and formal charges in CO₂

Atom Number Bonds Lone pairs Electrons round it Formal charge, V − N − B/2
C (central) 1 two double bonds 0 8 4 − 0 − 4 = 0
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 0, the molecule’s overall charge.

Minor resonance contributors to CO₂

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

C O O − +
+1 on the triple-bonded O and −1 on the single-bonded O. Its formal charges add up to more: 2 against 0.

Shape and polarity of CO₂

Central atom C
VSEPR class AX₂
Electron geometry linear
Molecular geometry linear
Ideal bond angle 180°
Measured bond angle 180°
Polarity, an estimate nonpolar

In a linear shape identical bonds cancel exactly.

C 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.

The measured angle is the accepted experimental value the VSEPR viewer quotes for this molecule.

Work with CO₂