Is SO3 Polar Or Nonpolar

sulfur trioxide polarity

Sulfur trioxide (SO3) is a chemical compound of sulfur and oxygen which has a colorless liquid. It can exist in the form of crystals, ice fibers, or as a gas. The compound name of SO3 is sulfur trioxide.

When SO3 is exposed to air, it quickly absorbs water and emits white fumes that smell very strongly and it’s dangerous to inhale. Sulfur trioxide (SO3) can react with water to form sulfuric acid.

Are you wondering is SO3 polar or nonpolar? This article will help you to clarify all your confusion about sulfur trioxide (SO3) polarity.

The sulfur trioxide (SO3) is corrosive to tissue and metals, and also, there is a fire risk if they come in contact with wood, cotton, etc.


The chemical formula of sulfur trioxide is SO3.

Common Name:

The sulfur trioxide is also called sulfuric anhydride and sulfuric oxide.

Is SO3 Polar Or Nonpolar

Explanation 1:

The sulfur trioxide (SO3) is a nonpolar molecule because, in SO3, electrons’ sharing is equal, and the lewis structure of SO3 appears to be an asymmetrical molecule.

Explanation 2:

The sulfur trioxide (SO3) is a nonpolar molecule because the shape of the SO3 is trigonal planar. The central atom in the trigonal planar molecule bonded to the three atoms and has no electron pairs. Therefore the total number of bonds becomes three, forming a bond angle of 120 degrees that cancel the polarity. Therefore SO3 is a nonpolar molecule.

Explanation 3:

The sulfur trioxide (SO3) is a nonpolar molecule because there are three molecules in S-O bonds, with no electron pairs. Also, due to the trigonal planar geometry, the SO3 is a nonpolar molecule.

Explanation 4:

The sulfur trioxide (SO3) is a nonpolar molecule because SO3 has a flat triangle geometry with D3h symmetry. Its net dipole moment is zero, and the moment of any two resultant vectors S-O is equal in its magnitude but opposite in direction to the third S-O moment. That is why sulfur trioxide (SO3) is considered a nonpolar molecule.

With that, it’s also essential to know about the NO2+ , NH4 and NF3 polarity.


Simple is that sulfur trioxide (SO3) is a nonpolar molecule. I have mentioned above why SO3 is nonpolar.

SO3 Molecular Geometry

SO3 Molecular Geometry
Molecular shape of SO3

The molecular geometry of SO3 is a trigonal planar with asymmetric charge distribution around the central atom. The bond angle of sulfur trioxide (SO3) is 120o.

You can see that all three S=O bonds are nearly double bonds in the above picture and all have the same length.

According to the VSEPR theory, you need to use the sigma bonds to establish the geometry. The three bonding pairs and no lone pairs on the central atom is equal to the trigonal planar.


Simple is that the molecular geometry of SO3 is trigonal planar.

SO3 Lewis Structure

Lewis dot structure of SO3
SO3 Lewis structure

To draw the Lewis structure of SO3, read the below instructions, and look at the above image to easily understand each step. As you can see in the picture, sulfur is in the center because of the lowest electron capability, and three oxygen is around the sulfur. 

  1. First of all, you need to count the valence electrons. Simple is that SO3 has 24 valence electrons.
  2. The reason why sulfur comes in the center is that it’s the least electronegative, put the sulfur in the center.
  3. Now put the more electronegative around the sulfur. Oxygen is more electronegative, so put it around the sulfur.
  4. Draw the six valence electrons in pairs of two around each atom.
  5. There are 12 electrons between the one sulfur and three oxygen atoms, as shown in Figure 5. They are highlighted green, which is easy to recognize.
  6. Draw the double, as shown in figure 6. If you want to make a single bond, it will take two electrons, and a double bond will take 4 electrons, and so on.
  7. The oxygen is more electronegative than sulfur because SO3 does not have a charge. That is why sulfur is considered weak if we compare it to oxygen. 
  8. The sulfide has two electrons, which belongs to the central sulfur atom. It’s possible because of octet rules, every atom wants a full valency shell, but in some situations, atoms lose electrons. The sulfide has a total number of 26, and sulfur has 24 valence electrons.

Are you still confused about the Lewis structure of SO3? Watch the video that will help you a lot.

Hybridization Of SO3

As you know that SO3 is a combination of sulfur and oxygen. If you want to understand the hybridization of SO3, you need to understand the bonding between oxygen and sulfur. If I talk about the lewis structure of SO3, so sulfur is in the center and has three double bonds with oxygen, which form one sigma and a pi bond. Therefore the hybridization of SO3 is sp2.

Essential Points To Remember During Hybridization:

  1. A double bond is created between the empty orbital sulfur and the empty orbital oxygen p.
  2. In sulfur trioxide (SO3), the sulfur will be on the central and have three double bonds with oxygen.
  3. In the sulfur, the sigma bond is between the sp2 orbitals.


Simple is that the hybridization of SO3 is sp2.

Is SO3 Ionic Or Covalent

The sulfur trioxide (SO3) is a covalent bond because, according to  Fajan’s rule, the chemical bonds with a positive charge atom mean it has more covalency of the bond than ionic. The SO3 has been present in the +6 oxidation state, so it’s more covalent and less ionic.


Simple is that sulfur trioxide (SO3) is a covalent not ionic.

Is SO3 A Base or Acid

Sulfur trioxide has two elements oxygen and sulfur. The oxygen atom of the water contains two lone pairs, so water is a Lewis base, and the sulfur has three electrons, which make SO3 Lewis acidic.

You can easily determine that it’s a base or acid. Follow the below instructions.

  • Before and after the reaction, count the hydrogens on each substance.
  • If you saw that the number of hydrogen is decreasing, then it means that the substance is base.
  • If you saw that the number of hydrogen is decreasing, then it means that the substance is acid.


In SO3, oxygen is Lewis base, and sulfur is Lewis acidic.

SO3 Dipole Moment

SO3 has no dipole moment because SO3 is trigonal planar, so S-O bonds cancel, resulting in no dipole moment.


The SO3 has no dipole moment.

Related Questions

Does so3 violate the octet rule?

Yes, SO3 violates the octet rules, and it doesn’t follow octet rules because SO3 forms three double bonds with oxygen atoms, where 12 electrons are obtained from the oxygen.

Is dative bond present in so3?

The SO3 doesn’t show dative bonding because the structure of SO3 is not stable, that carries a formal charge. The NH3 shows a dative bond because alone pairs of electrons in the NH3 are present in the central nitrogen atom.

What is so3 2 called?

The SO3 2 is called Sulfite.

Final Thoughts

That was all about is SO3 polar or nonpolar. I hope you may now be understood that SO3 is a nonpolar molecule.

The SO3 is a nonpolar because of many reasons, which I have explained above in details.

The molecular geometry of SO3 is trigonal planar, Above is the lewis structure of SO3 video and theoretical explanation. If you didn’t understand theoretically to draw the lewis structure, then watch the video.

The hybridization of SO3 is sp2.

Do you think we have missed something about the SO3 polarity topic? Let us know in the comments section below I will update the article.

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