Lewis structure of CO2

The Lewis structure of CO₂ illustrates the bonding and electron distribution in carbon dioxide, a compound consisting of one carbon atom and two oxygen atoms.^[1][2][3][4] In this structure, the central carbon atom forms double bonds with each of the two oxygen atoms. Each oxygen atom possesses two lone pairs of electrons, whereas the carbon atom has no lone pairs.^[5][6][7][8] All atoms satisfy the octet rule, indicating a stable structure with no formal charges on any of the atoms.^{[9][10][11][12]}

The accurate Lewis structure of CO₂ can be drawn in five simple steps. First, calculate the total number of valence electrons and select the central atom, which is the least electronegative among the atoms in CO₂.^{[13][14][15][16]} Use this information to create a rough sketch of the molecule, showing the arrangement of atoms. Next, place electron pairs between the atoms in the sketch to represent the chemical bonds. Then, determine the total number of lone pairs and distribute them on the atoms, starting with the outer atoms and moving to the central atom to ensure proper distribution. After that, check whether each atom adheres to the octet rule. If any atom does not have a complete octet, adjust the lone pairs to form multiple bonds as needed. Finally, calculate the formal charge for each atom, indicate these charges on the atoms, and verify whether the structure is stable.

Alternative method: CO₂ 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 CO₂ has one carbon atom and two oxygen atoms.

So the total number of valence electrons = valence electrons of carbon atom + (valence electrons of oxygen atom × 2)

Therefore, the total number of valence electrons = 4 + 12 = 16

• 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 in the center and oxygens on either side. And draw the rough skeleton structure for the Lewis structure of CO₂ something like this:

Also read: How to draw Lewis structure of H₂O (4 steps)

Show chemical bond

Place two electrons between the atoms to show a chemical bond. Since carbon is surrounded by two oxygens, use four electrons to show two chemical bonds as follows:

Mark lone pairs

As calculated earlier, we have a total of 16 valence electrons. And in the above structure, we have already used four valence electrons. Hence, twelve valence electrons are remaining.

Two valence electrons represent one lone pair. So twelve valence electrons = six 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 atoms are oxygens, so each oxygen will get three lone pairs. And the central atom (carbon) will not get any lone pair, because all six lone pairs are used.

So the Lewis structure of CO₂ looks something like this:

In the above structure, you can see that the octet is completed on outside atoms. 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 NO₂ (5 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 one lone pair from each oxygen atom to make a new bond with the carbon atom. And then, the Lewis structure of CO₂ 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 atoms. 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 NH₃ (4 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 = 0
Bonding electrons = 8

Formal charge = 4 – 0 – ½ (8) = 0

• For each oxygen atom

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

Formal charge = 6 – 4 – ½ (4) = 0

Mention the formal charges of atoms on the structure. So the Lewis structure of CO₂ looks something like this:

In the above structure, you can see that the formal charges of both (carbon and oxygen) are zero. Therefore, this is the stable Lewis structure of CO₂.

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

Next: Lewis structure of H₂O

Related

• Lewis structure of H₂O
• Lewis structure of NO₂
• Lewis structure of NH₃
• Lewis structure of HCN
• Lewis structure of SO₂

References