SOCl2 Lewis structure

SOCl₂ (thionyl chloride) has one sulfur atom, one oxygen atom, and two chlorine atoms.

In the SOCl₂ Lewis structure, there are two single bonds and one double bond around the sulfur atom, with two chlorine atoms and one oxygen atom attached to it. Each chlorine atom has three lone pairs, the oxygen atom has two lone pairs, and the sulfur atom has one lone pair.

Alternative method: Lewis structure of SOCl₂

Rough sketch

• First, determine the total number of valence electrons

In the periodic table, both sulfur and oxygen lie in group 16, and chlorine lies in group 17.

Hence, both sulfur and oxygen have six valence electrons, and chlorine has seven valence electrons.

Since SOCl₂ has one sulfur atom, one oxygen atom, and two chlorine atoms, so…

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

And the total valence electrons = 6 + 6 + 14 = 26

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

• Second, find the total electron pairs

We have a total of 26 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 = 26 ÷ 2 = 13

• Third, determine the central atom

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

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

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

• And finally, draw the rough sketch

Lone pair

Here, we have a total of 13 electron pairs. And three bonds are already marked. So we have to only mark the remaining ten electron pairs as lone pairs on the sketch.

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

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

So for oxygen and each chlorine, there are three lone pairs, and for sulfur, there is one lone pair.

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 sulfur atom, formal charge = 6 – 2 – 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 sulfur and oxygen atoms have charges, so mark them on the sketch as follows:

The above structure is not a stable Lewis structure because both sulfur 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 S — O bond with the sulfur atom as follows:

Final structure

The final structure of SOCl₂ comprises a central sulfur atom connected to one oxygen atom and two chlorine atoms. In this layout, the sulfur atom utilizes an expanded valence shell to form a double bond with the oxygen atom and single bonds with each chlorine atom, while also retaining one lone pair. The oxygen atom reaches its octet with two lone pairs, and both chlorine atoms satisfy their octets by maintaining three lone pairs each. This specific arrangement is the most stable because it results in a formal charge of zero for all atoms, which represents the most energetically favorable electronic state. Thus, this specific electronic distribution serves as the definitive and most accurate Lewis representation of thionyl chloride.

Next: POCl₃ Lewis structure

External video

• SOCl2 Lewis Structure – How to Draw the Lewis Structure for SOCl2 – YouTube • Wayne Breslyn

External links

• https://lambdageeks.com/socl2-lewis-structure/
• https://topblogtenz.com/thionyl-chloride-socl2-lewis-dot-structure-and-molecular-geometry/
• https://www.thegeoexchange.org/chemistry/bonding/Lewis-Structures/SOCl2-lewis-structure.html