CO2 Lewis Structure
The Lewis dot structure of carbon dioxide (CO2): carbon in the centre, a double bond to each oxygen, and two lone pairs on each oxygen.
How to draw the Lewis structure of CO2
- Count valence electrons: C has 4, each O has 6, so the total is 4 + 2 × 6 = 16 electrons.
- Put the least electronegative atom, carbon, in the centre and join each oxygen to it with a single bond (4 electrons used).
- Share out the remaining 12 electrons as lone pairs on the oxygens: 3 pairs on each. Now each oxygen has 8, but carbon only has 4.
- Move one lone pair from each oxygen into a second bond with carbon. Two double bonds give carbon 8 electrons, and each oxygen keeps 2 lone pairs + 1 double bond = 8.
Worked example: checking formal charges
Formal charge = valence electrons − lone-pair electrons − bonds. For carbon: 4 − 0 − 4 = 0. For each oxygen: 6 − 4 − 2 = 0. Every atom has a formal charge of zero, which is why O=C=O is the best structure (the alternative O≡C–O would give +1 and −1 charges on the oxygens).
Compare it with the N2 Lewis structure (a triple bond) and the VSEPR chart for why two electron domains make a straight line, then build CO2 in 3D in the Constructeur de Molécules.
Foire aux questions
How many valence electrons does CO2 have?
Sixteen. Carbon has 4 and each oxygen has 6, so 4 + 6 + 6 = 16 valence electrons.
Why does CO2 have double bonds and not single bonds?
With single bonds, carbon would only have 4 electrons around it. Turning one lone pair on each oxygen into a second bond gives carbon a full octet (two double bonds = 8 electrons) and keeps every oxygen at 8 too.
What is the shape of CO2?
Linear, with a 180° O=C=O bond angle. Carbon has two electron domains (the two double bonds) and no lone pairs, so they point in opposite directions.
Is CO2 polar or nonpolar?
Nonpolar. Each C=O bond is polar because oxygen is more electronegative, but the two bond dipoles point in opposite directions and cancel in the straight molecule.
