COCl2 Lewis structure

COCl₂ (phosgene) has one carbon atom, one oxygen atom, and two chlorine atoms.

In the COCl₂ Lewis structure, there are two single bonds and one double bond around the carbon atom, with two chlorine atoms and one oxygen atom attached to it. Two chlorine atoms with single bonds have three lone pairs, and one oxygen atom with a single bond has two lone pairs.

Alternative method: Lewis structure of COCl₂

Rough sketch

• First, determine the total number of valence electrons

In the periodic table, carbon lies in group 14, oxygen lies in group 16, and chlorine lies in group 17.

Hence, carbon has four valence electrons, oxygen has six valence electrons, and chlorine has seven valence electrons.

Since COCl₂ has one carbon atom, one oxygen atom, and two chlorine atoms, so…

Valence electrons of one carbon atom = 4 × 1 = 4
Valence electrons of one oxygen atom = 6 × 1 = 6
Valence electrons of two chlorine atoms = 7 × 2 = 14

And the total valence electrons = 4 + 6 + 14 = 24

Learn how to find: Carbon valence electrons, Oxygen valence electrons, and Chlorine valence electrons

• Second, find the total electron pairs

We have a total of 24 valence electrons. And when we divide this value by two, we get the value of total electron pairs.

Total electron pairs = total valence electrons ÷ 2

So the total electron pairs = 24 ÷ 2 = 12

• Third, determine the central atom

We have to place the least electronegative atom at the center.

Since carbon is less electronegative than oxygen and chlorine, assume that the central atom is carbon.

Therefore, place carbon in the center and oxygen and chlorine on either side.

• And finally, draw the rough sketch

Lone pair

Here, we have a total of 12 electron pairs. And three bonds are already marked. So we have to only mark the remaining nine electron pairs as lone pairs on the sketch.

Also remember that both (carbon and oxygen) are the period 2 elements, so they can not keep more than 8 electrons in their last shell. And chlorine is a period 3 element, so it can keep more than 8 electrons in its last shell.

Always start to mark the lone pairs from outside atoms. Here, the outside atoms are chlorine and oxygen.

So for each chlorine and oxygen, there are three lone pairs, and for carbon, there is zero lone pair because all nine electron pairs are over.

Mark the lone pairs on the sketch as follows:

Formal charge

Use the following formula to calculate the formal charges on atoms:

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

For carbon atom, formal charge = 4 – 0 – ½ (6) = +1

For oxygen atom, formal charge = 6 – 6 – ½ (2) = -1

For each chlorine atom, formal charge = 7 – 6 – ½ (2) = 0

Here, both carbon and oxygen atoms have charges, so mark them on the sketch as follows:

The above structure is not a stable Lewis structure because both carbon and oxygen atoms have charges. Therefore, reduce the charges (as below) by converting lone pairs to bonds.

Convert a lone pair of the oxygen atom to make a new C — O bond with the carbon atom as follows:

Final structure

The final structure of COCl₂ contains a central carbon atom connected to an oxygen atom and two chlorine atoms. In this arrangement, the carbon atom forms a double bond with the oxygen atom and single covalent bonds with each of the two chlorine atoms to achieve a stable octet. Within this layout, the oxygen atom satisfies the octet rule by maintaining two lone pairs alongside its double bond, while each chlorine atom fulfills its octet by retaining three lone pairs. This configuration represents the most stable state for the molecule because it results in a formal charge of zero for every atom involved. Accordingly, this specific electronic distribution serves as the definitive and most accurate Lewis representation of phosgene.

Next: BrF₅ Lewis structure

External video

• COCl2 Lewis Structure – How to Draw the Lewis Structure for COCl2 – YouTube • Wayne Breslyn

External links

• https://techiescientist.com/cocl2-lewis-structure/
• https://www.thegeoexchange.org/chemistry/bonding/Lewis-Structures/COCl2-lewis-structure.html
• https://topblogtenz.com/cocl2-lewis-structure-molecular-geometry-hybridization-polarity/
• https://lambdageeks.com/cocl2-lewis-structure/
• https://geometryofmolecules.com/cocl2-lewis-structure-molecular-structure-hybridization-bond-angle-and-shape/