SO Lewis Structure

SO Lewis Structure

SO (sulfur monoxide) has one sulfur atom and one oxygen atom. In the lewis structure of SO, there is a double bond between the sulfur and oxygen atom, and on both sulfur and oxygen atoms, there are two lone pairs.


Here’s how you can draw the SO lewis structure step by step.

Step #1: draw sketch
Step #2: mark lone pairs
Step #3: mark charges
Step #4: minimize charges
Step #5: minimize charges again (if there are)

Let’s break down each step in detail.

#1 Draw Sketch

  • First, determine the total number of valence electrons

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

Hence, both sulfur and oxygen have six valence electrons.

Since SO has one sulfur atom and one oxygen atom, so…

Valence electrons of one sulfur atom = 6 × 1 = 6
Valence electrons of one oxygen atom = 6 × 1 = 6

And the total valence electrons = 6 + 6 = 12

  • Second, find the total electron pairs

We have a total of 12 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 = 12 ÷ 2 = 6

  • Third, determine the central atom

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

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

  • And finally, draw the rough sketch
SO Lewis Structure (Step 1)

#2 Mark Lone Pairs

Here, we have a total of 6 electron pairs. And one S — O bond is already marked. So we have to only mark the remaining five electron pairs as lone pairs on the sketch.

Also remember that sulfur is a period 3 element, so it can keep more than 8 electrons in its 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 atom is oxygen.

So for oxygen, there are three lone pairs, and for sulfur, there are two lone pairs.

Mark the lone pairs on the sketch as follows:

SO Lewis Structure (Step 2)

#3 Mark Charges

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 – 4 – ½ (2) = +1

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

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

SO Lewis Structure (Step 3)

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.

#4 Minimize Charges

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

SO Lewis Structure (Step 4)

In the above structure, you can see that the central atom (sulfur) forms an octet. Hence, the octet rule is satisfied.

Also, the above structure is more stable than the previous structures. Therefore, this structure is the stable lewis structure of SO.

Next: S2O Lewis Structure

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