Lewis structure of CO

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The Lewis structure of CO illustrates the molecular arrangement of carbon monoxide, a compound with one carbon atom and one oxygen atom. In this structure, the carbon atom forms a triple bond with the oxygen atom. Both the carbon and the oxygen atoms have one lone pair of electrons. While both atoms satisfy the octet rule, formal charges are present. In the most stable Lewis structure of CO, the carbon atom has a negative (-1) formal charge, while the oxygen atom has a positive (+1) formal charge.

Alternative method: CO Lewis structure

Steps

Draw skeleton

In this step, first calculate the total number of valence electrons. And then, decide the central atom.

• Let’s calculate the total number of valence electrons

We know that… carbon is a group 14 element and oxygen is a group 16 element. Hence, carbon has four valence electrons and oxygen has six valence electrons.

Now CO has one carbon atom and one oxygen atom.

So the total number of valence electrons = valence electrons of carbon atom + valence electrons of oxygen atom

Therefore, the total number of valence electrons = 4 + 6 = 10

• Now decide the central atom

The atom with the least electronegative value is placed at the center. By looking at the periodic table, we get the electronegativity values for carbon and oxygen as follows:

Electronegativity value of carbon = 2.55
Electronegativity value of oxygen = 3.44

Obviously, carbon is less electronegative than oxygen. Hence, assume that carbon is the central atom.

So now, put carbon and oxygen next to each other. And draw the rough skeleton structure for the Lewis structure of CO something like this:

Also read: How to draw Lewis structure of C₂H₄ (5 steps)

Show chemical bond

Place two electrons between the atoms to show a chemical bond as follows:

Mark lone pairs

As calculated earlier, we have a total of 10 valence electrons. And in the above structure, we have already used two valence electrons. Hence, eight valence electrons are remaining.

Two valence electrons represent one lone pair. So eight valence electrons = four lone pairs.

Note that both (carbon and oxygen) are the period 2 elements, so they can not keep more than 8 electrons in their last shell.

Also, make sure that you start marking these lone pairs on outside atoms first. And then, on the central atom.

The outside atom is oxygen, so oxygen will get three lone pairs. And the central atom (carbon) will get one lone pair.

So the Lewis structure of CO looks something like this:

In the above structure, you can see that the octet is completed on the outside atom. But, the central atom (carbon) doesn’t form an octet.

So in the next step, we have to complete the octet on the central atom.

Also read: How to draw Lewis structure of BF₃ (4 steps)

Complete octet on central atom

Remember that carbon is a period 2 element, so it can not keep more than 8 electrons in its last shell.

Now carbon already has four valence electrons. Hence, carbon needs four more valence electrons to complete its octet.

So convert two lone pairs from the oxygen atom to make a new bond with the carbon atom. And then, the Lewis structure of CO looks something like this:

In the above structure, you can see that the octet is completed on the central atom (carbon), and also on the outside atom. Therefore, the octet rule is satisfied.

After completing the octet, one last thing we need to do is, calculate the formal charge and check the stability of the above structure.

Also read: How to draw Lewis structure of SO₃ (6 steps)

Calculate formal charge and check stability

The following formula is used to calculate the formal charges on atoms:

Formal charge = valence electrons – nonbonding electrons – ½ bonding electrons

Collect the data from the above structure and then, write it down below as follows:

• For carbon atom

Valence electrons = 4
Nonbonding electrons = 2
Bonding electrons = 6

Formal charge = 4 – 2 – ½ (6) = -1

• For oxygen atom

Valence electrons = 6
Nonbonding electrons = 2
Bonding electrons = 6

Formal charge = 6 – 2 – ½ (6) = +1

Mention the formal charges of atoms on the structure. So the Lewis structure of CO looks something like this:

In the above structure, you can see that the formal charges of atoms are closer to zero. Therefore, this is the most stable Lewis structure of CO.

And each horizontal line drawn in the above structure represents a pair of bonding valence electrons.

Next: Lewis structure of C₂H₄

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Related

• Lewis structure of C₂H₄
• Lewis structure of BF₃
• Lewis structure of SO₃
• Lewis structure of O₃
• Lewis structure of H₂S

External video

• How to Draw the Lewis Dot Diagram for Carbon monoxide (CO) – YouTube • Wayne Breslyn

External links

• Lewis Structure for CO – The University of Maryland
• CO Lewis structure, Hybridization, and Molecular Geometry (Carbon Monoxide) – Geometry of Molecules
• How can I draw the Lewis structure for CO? – Socratic
• CO Lewis Structure in 5 Steps (With Images) – Pediabay
• Carbon monoxide (CO) Molecule Lewis Structure – Chemistry School
• CO molecular geometry, lewis structure, hybridization, bond angle – Topblogtenz
• CO Lewis structure in 6 steps (With Images) – Chemistry Online
• CO Lewis Structure, Geometry – Kemicalinfo
• CO Lewis Structure & Molecular Geometry – What’s Insight
• What is the Lewis Structure of CO? – Quora
• Draw the Lewis structure of CO. Include lone pairs – Chegg
• CO Lewis Structure, Geometry, and Hybridization – Techiescientist
• Chemical Bonding: CO Lewis Structure – The Geoexchange
• MO diagram and Lewis Structure of CO – Laurence Lavelle
• Draw the Lewis structure for CO – Homework.Study.com
• Why does Lewis dot structure of CO not have formal charges close to 0? – Chemistry Stack Exchange
• Formal Charge of Carbon Monoxide (CO) – Chemistry Learner