COCl2 Lewis Structure in 6 Steps (With Images)

So you have seen the above image by now, right?

Let me explain the above image in short.

COCl2 lewis structure has a Carbon atom (C) at the center which is surrounded by two Chlorine atoms (Cl) and one Oxygen atom (O). There is a double bond between the Carbon (C) & Oxygen (O) atom and a single bond between the Carbon (C) and Chlorine (Cl) atoms.

If you haven’t understood anything from the above image of COCl2 lewis structure, then just stick with me and you will get the detailed step by step explanation on drawing a lewis structure of COCl2.

So let’s move to the steps of drawing the lewis structure of COCl2.

Steps of drawing COCl2 lewis structure

Step 1: Find the total valence electrons in COCl2 molecule

In order to find the total valence electrons in a COCl2 molecule, first of all you should know the valence electrons present in carbon atom, oxygen atom as well as chlorine atom.
(Valence electrons are the electrons that are present in the outermost orbit of any atom.)

Here, I’ll tell you how you can easily find the valence electrons of carbon, oxygen as well as chlorine using a periodic table.

Total valence electrons in COCl2 molecule

→ Valence electrons given by carbon atom:

Carbon is group 14 element on the periodic table. ^[1] Hence the valence electrons present in carbon is 4.

You can see the 4 valence electrons present in the carbon atom as shown in the above image.

→ Valence electrons given by oxygen atom:

Oxygen is group 16 element on the periodic table. ^[2] Hence the valence electrons present in oxygen is 6.

You can see the 6 valence electrons present in the oxygen atom as shown in the above image.

→ Valence electrons given by chlorine atom:

Chlorine is group 17 element on the periodic table. ^[3] Hence the valence electrons present in chlorine is 7.

You can see the 7 valence electrons present in the chlorine atom as shown in the above image.

Hence, 

Total valence electrons in COCl2 molecule = valence electrons given by 1 carbon atom + valence electrons given by 2 oxygen atoms + valence electrons given by 2 chlorine atoms = 4 + 6 + 7(2) = 24.

Step 2: Select the central atom

For selecting the center atom, you have to remember that the atom which is less electronegative remains at the center.

Now here the given molecule is COCl2 and it contains carbon atom (C), oxygen atom (O) and chlorine atoms (Cl).

You can see the electronegativity values of carbon atom (C), oxygen atom (O) and chlorine atoms (Cl) in the above periodic table.

If we compare the electronegativity values of carbon atom (C), oxygen atom (O) and chlorine atoms (Cl) then the carbon atom is less electronegative.

So here the carbon atom is the center atom and the oxygen & chlorine atoms are the outside atoms.

Step 3: Connect each atoms by putting an electron pair between them

Now in the COCl2 molecule, you have to put the electron pairs between the carbon (C) & oxygen (O) atom and between the carbon (C) & chlorine (Cl) atoms.

This indicates that these atoms are chemically bonded with each other in a COCl2 molecule.

Step 4: Make the outer atoms stable

Now in this step, you have to check the stability of the outer atoms.

Here in the sketch of COCl2 molecule, you can see that the outer atoms are oxygen atom and chlorine atoms.

These oxygen atom and chlorine atoms are forming an octet and hence they are stable.

Also, in step 1 we have calculated the total number of valence electrons present in the COCl2 molecule.

The COCl2 molecule has a total 24 valence electrons and all these valence electrons are used in the above sketch of COCl2.

Hence there are no remaining electron pairs to be kept on the central atom. 

So now let’s proceed to the next step.

Step 5: Check the octet on the central atom. If it does not have octet, then shift the lone pair to form a double bond or triple bond.

In this step, you have to check whether the central carbon atom (C) is stable or not.

In order to check the stability of the central carbon (C) atom, we have to check whether it is forming an octet or not.

Unfortunately, the carbon atom is not forming an octet here. Carbon has only 6 electrons and it is unstable.

Now to make this carbon atom stable, you have to shift the electron pair from the outer oxygen atom so that the carbon atom can have 8 electrons (i.e octet).

After shifting this electron pair, the central carbon atom will get 2 more electrons and thus its total electrons will become 8.

You can see from the above picture that the carbon atom is forming an octet as it has 8 electrons.

Now let’s proceed to the final step to check whether the lewis structure of COCl2 is stable or not.

Step 6: Check the stability of lewis structure

Now you have come to the final step in which you have to check the stability of lewis structure of COCl2.

The stability of lewis structure can be checked by using a concept of formal charge.

In short, now you have to find the formal charge on carbon (C) atom, oxygen (O) atom as well as chlorine (Cl) atoms present in the COCl2 molecule.

For calculating the formal charge, you have to use the following formula;

Formal charge = Valence electrons – (Bonding electrons)/2 – Nonbonding electrons

You can see the number of bonding electrons and nonbonding electrons for each atom of COCl2 molecule in the image given below.

For Carbon (C) atom:
Valence electrons = 4 (because carbon is in group 14)
Bonding electrons = 8
Nonbonding electrons = 0

For Oxygen (O) atom:
Valence electrons = 6 (because oxygen is in group 16)
Bonding electrons = 4
Nonbonding electrons = 4

For Chlorine (Cl) atom:
Valence electron = 7 (because chlorine is in group 17)
Bonding electrons = 2
Nonbonding electrons = 6

Formal charge	=	Valence electrons	–	(Bonding electrons)/2	–	Nonbonding electrons
C	=	4	–	8/2	–	0	=	0
O	=	6	–	4/2	–	4	=	0
Cl	=	7	–	2/2	–	6	=	0

From the above calculations of formal charge, you can see that the carbon (C) atom, oxygen (O) atom as well as chlorine (Cl) atoms have a “zero” formal charge.

This indicates that the above lewis structure of COCl2 is stable and there is no further change in the above structure of COCl2.

In the above lewis dot structure of COCl2, you can also represent each bonding electron pair (:) as a single bond (|). By doing so, you will get the following lewis structure of COCl2.

(Note: In step 5, if we had moved the electron pair from the chlorine atom, then there will be +1 and -1 charges on chlorine and oxygen respectively. But here we move the electron pair from the oxygen atom, which gives the more stable structure (having “zero” charges on all the atoms.))

I hope you have completely understood all the above steps.

For more practice and better understanding, you can try other lewis structures listed below.

Try (or at least See) these lewis structures for better understanding:

NCl3 lewis structure	CHCl3 lewis structure
BrF3 lewis structure	SF2 lewis structure
IF5 lewis structure	HNO3 lewis structure