What is the Charge on SO3? And Why?

The Charge of SO3 is 0.

But the question is how can you say that the charge on SO3 (Sulfur trioxide) is 0?

Well you can say this by calculating its formal charge.

So let’s calculate the formal charge of SO3 (Sulfur trioxide).

If you are a visual learner like me, then here is a short two minute video for you.

Calculating the formal charge of SO3 using lewis structure

In order to calculate the formal charge on SO3 (Sulfur trioxide), you should know the Lewis dot structure of SO3 (Sulfur trioxide).

Here is the lewis structure of SO3.

Now using the above lewis structure of SO3, you have to find the formal charge on each atom that is present in the SO3 molecule.

For calculating the formal charge, you need to remember this formula;

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

You can see the bonding and nonbonding electrons of SO3 from the image given below.

So now let’s calculate the formal charge on each individual atom present in SO3.

Formal charge on Sulfur atom:
Valence electrons = 6 (as it is in group 16 on periodic table) ^[1]
Nonbonding electrons = 0
Bonding electrons = 12

So according to the formula of formal charge, you will get;

Formal charge on Sulfur = Valence electrons – Nonbonding electrons – (Bonding electrons)/2 = 6 – 0 – (12/2) = 0

So the formal charge on sulfur atom is 0.

Formal charge on Oxygen atom:
Valence electrons = 6 (as it is in group 16 on periodic table) ^[2]
Nonbonding electrons = 4
Bonding electrons = 4

So according to the formula of formal charge, you will get;

Formal charge on Oxygen = Valence electrons – Nonbonding electrons – (Bonding electrons)/2 = 6 – 4 – (4/2) = 0

So the formal charge on oxygen atom is 0.

Now you can see that all the atoms of SO3 have 0 formal charge. 

This indicates that the overall SO3 (Sulfur trioxide) molecule also has 0 charge and hence it is a neutral molecule.

I hope you have understood the above calculations for the formal charge of SO3 (Sulfur trioxide). 

Check out some other related topics for your practice.

Related topics:
Charge on CO2
Charge on H2O (Water)
Charge on ClO4 (Perchlorate ion)
Charge of Manganese (Mn)
Charge of Strontium (Sr)