CO Lewis Structure

Carbon monoxide · The colourless, odourless product of incomplete combustion.

• 10 valence e−
• linear
• sp
• polar

Calculated properties

How to draw the CO Lewis structure

Step through it. The bar shows how much of the 10-electron budget is spent at each stage - it never grows, which is the whole constraint.

The reasoning at each step

1. Count the valence electrons

   Add up the outer-shell electrons every atom brings. That total is the budget for the whole structure - every line and every dot has to come out of it, and nothing may be added.

   4 (C) + 6 (O) = 10 valence electrons

2. Work out what is bonded to what

   Two atoms, one connection. The only question is the bond order.

3. Join everything with single bonds first

   Every connection starts as one shared pair. Draw them all before worrying about double bonds - the arithmetic in the next step is what tells you where the double bonds have to go.

   1 bond x 2 = 2 electrons used, 8 left

4. Work out how far short you are

   Add up what every atom still needs to fill its shell - eight electrons for most atoms, two for hydrogen - minus what its single bonds already give it. Compare that with the electrons you have left. The difference decides everything that follows.

   needs 12, has 8, short by 4

5. Turn the shortfall into multiple bonds

   Being short means atoms have to share more. Every pair that moves from a lone pair into a bond counts twice - once for each atom - so a shortfall of 4 is covered by 2 extra shared pairs. That is where the triple bond comes from.

   C#O

6. Fill in the lone pairs

   Every electron not in a bond sits as a lone pair on an atom. Each atom takes exactly what it needs to finish its shell - there is no choice left at this point.

   C: 1, O: 1 (4 electrons)

7. Check the formal charges

   Formal charge is valence electrons, minus lone-pair electrons, minus the number of bonds. They are not real charges, but they have to add up to the overall charge on the species, and a structure that keeps them small is the better one.

   C: 4 - 2 - 3 = -1 ; O: 6 - 2 - 3 = +1

8. Work out the shape

   Count the electron domains on C: 1 bonded group plus 1 lone pair. A double or triple bond still counts as one domain, because it points in one direction. That gives linear electron geometry; ignore the lone pairs and the atoms themselves sit in a linear arrangement. Two atoms can only lie in a straight line, so there is no bond angle to measure.

   steric number 2 -> sp -> linear

9. Decide whether it is polar

   The atoms around the centre are not all the same, so the bond dipoles are different sizes and cannot cancel.

   dipoles do not cancel -> polar

Is CO polar or nonpolar?

CO is polar. The atoms around the centre are not all the same, so the bond dipoles are different sizes and cannot cancel.

Common questions

How many valence electrons does CO have?

CO has 10 valence electrons. 6 of them are in bonds and 4 sit in lone pairs.

What is the molecular geometry of CO?

CO is a linear molecule. The central C has 1 bonded group and one lone pair, a steric number of 2, which gives linear electron geometry and a linear molecule.

What is the hybridization of CO?

The central C in CO is sp hybridized. Steric number 2 means 2 orbitals have to be mixed, which is exactly what sp gives you.

Is CO polar or nonpolar?

CO is polar. The atoms around the centre are not all the same, so the bond dipoles are different sizes and cannot cancel.

Related molecules

• CO₂ also built around C
• C₂H₂ also built around C
• HCN also built around C
• N₂ also linear
• N₂O also linear
• O₂ also linear