Lewis Structure for CO

[Karina Patel 1N]

For problem 2.49 part c: Draw a Lewis structure and determine the formal charge on each atom: c) CO

When modeling the Lewis Structure for CO, why would you form a triple bond to create a formal charge of +1 on Oxygen and -1 on Carbon?

If we were to use a double bond, then the formal charge on both Carbon and Oxygen would be 0. I thought the objective was to have the formal charge as 0 if possible?

[Brandon Jarrold4H]

Hi Karina, Good Question!

Keep in mind, that carbon has 4 valence electrons and oxygen has 6 valence electrons totaling 10 electrons in the Lewis model. A double bond would create 12 electrons, however a triple bond creates 10 electrons, still in octet form. Thus a triple bond is the only answer for this model.

[Victor Qiu 1C]

C has 4 valences electrons, O has 6 valence electrons. If there is a double bond in CO, C still needs 2 pairs of lone pair electrons to satisfy octet rule, and O also needs 2 pairs of lone pair electrons to satisfy the octet rule. Therefore, in total there should be 2×2+2×2+2×2=12 electrons. However, CO only has 4+6=10 electrons, so it should not form a double bond, but should form a triple bond.

[Aria Movassaghi 1A]

You typically want formal charge of zero but O and C need to satisfy the octet rule. Therefore you need to use a triple bond because you have a total of 10 valence electrons to use.