Is SO3 Ionic or Covalent? (And Why?)

Is SO3 Ionic or Covalent

SO3 is a covalent (nonpolar covalent) compound because when one nonmetal combines with another nonmetal, it usually forms a covalent compound. Here, S is a nonmetal and O is also a nonmetal. So when they combine, it forms a covalent compound.

Well, now you have got to know that SO3 is a covalent compound, but let me explain the in-depth reason why SO3 is a covalent compound.

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

Why is SO3 a Covalent compound?

As mentioned above, you can simply remember that when the nonmetal combines with another nonmetal, the bond between them is a covalent bond.

Here in SO3, the S atom is a nonmetal and the O atom is also a nonmetal.

Hence the bond between them is a covalent bond.

Is SO3 polar covalent or nonpolar covalent?

In order to know whether SO3 is a polar covalent molecule or nonpolar covalent molecule, we have to check the electronegativity difference of the combining atoms.

If the electronegativity difference (ΔEN) is less than 0.4, then the bond is nonpolar covalent bond. 

If the electronegativity difference (ΔEN) is between 0.4 to 1.7, then the bond is polar covalent bond. [1] [2] [3] [4] [5]

Now the electronegativity of Sulfur and Oxygen are mentioned below. (You can see the electronegativity of all the elements from this electronegativity chart).

  • Electronegativity of Sulfur (S) = 2.58
  • Electronegativity of Oxygen (O) = 3.44

So for SO3, the electronegativity difference (ΔEN) = 3.44 – 2.58 = 0.86

This value lies between 0.4 to 1.7, which indicates that the bond between Sulfur (S) and Oxygen (O) is polar covalent bond.

But if you look at the 3D structure of SO3, you can see that the structure of SO3 is symmetrical.

As the bonds (S=O) are symmetrical and the SO3 molecule has a symmetrical geometry, their bond polarity gets canceled with each other.


Hence, SO3 is a nonpolar covalent molecule.

I hope you have understood the reason why SO3 is a nonpolar covalent compound.

Check out other compounds to see whether they are ionic or covalent;
Is CaF2 Ionic or Covalent?
Is K2O Ionic or Covalent?
Is KBr Ionic or Covalent?
Is KI Ionic or Covalent?
Is CaCO3 Ionic or Covalent? 


Jay is an educator and has helped more than 100,000 students in their studies by providing simple and easy explanations on different science-related topics. With a desire to make learning accessible for everyone, he founded Knords Learning, an online learning platform that provides students with easily understandable explanations.

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