C2Cl2 Lewis structure

C₂Cl₂ (dichloroacetylene) has two carbon atoms and two chlorine atoms.

In the C₂Cl₂ Lewis structure , there is a triple bond between the two carbon atoms, and each carbon is attached with one chlorine atom, and on each chlorine atom, there are three lone pairs.

Alternative method: Lewis structure of C₂Cl₂

Rough sketch

• First, determine the total number of valence electrons

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

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

Since C₂Cl₂ has two carbon atoms and two chlorine atoms, so…

Valence electrons of two carbon atoms = 4 × 2 = 8
Valence electrons of two chlorine atoms = 7 × 2 = 14

And the total valence electrons = 8 + 14 = 22

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

• Second, find the total electron pairs

We have a total of 22 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 = 22 ÷ 2 = 11

• Third, determine the central atom

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

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

Here, there are two carbon atoms, so we can assume any one as the central atom.

Let’s assume that the central atom is right carbon.

Therefore, place carbons in the center and chlorines on either side.

• And finally, draw the rough sketch

Lone pair

Here, we have a total of 11 electron pairs. And three bonds are already marked. So we have to only mark the remaining eight electron pairs as lone pairs on the sketch.

Also remember that carbon is a period 2 element, so it can not keep more than 8 electrons in its 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 chlorines and left carbon.

So for each chlorine, there are three lone pairs, for left carbon, there are two lone pairs, and for right carbon, there is zero lone pair because all eight 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 left carbon atom, formal charge = 4 – 4 – ½ (4) = -2

For right carbon atom, formal charge = 4 – 0 – ½ (4) = +2

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

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

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

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

Since there are charges on both carbon atoms, again convert a lone pair of the left carbon atom to make a new C — C bond with the right carbon atom as follows:

Final structure

The final structure of C₂Cl₂ comprises two central carbon atoms linked by a triple covalent bond, with each carbon also connected to a chlorine atom via a single covalent bond. Within this layout, both carbon atoms achieve a full octet by forming four bonds in total—three with the neighboring carbon and one with a chlorine atom. Each chlorine atom satisfies the octet rule by retaining three lone pairs alongside its single bonding pair. This linear configuration is the most stable because it yields a formal charge of zero for every atom, representing the most energetically favorable state for the molecule. Thus, this specific electronic distribution serves as the definitive and most accurate Lewis representation of dichloroacetylene.

Next: NO₄^3- Lewis structure

External video

• C2Cl2 Lewis Structure: How to Draw the Lewis Structure for C2Cl2 – YouTube • Wayne Breslyn