Hybridization of SO₂

What is SO2 Hybridisation?

In sulphur dioxide (SO2), the hybridization type that takes place is sp2. To describe this, let us first look at the sulphur atom, which will be the SO2 hybridization of the central atom. At the time of SO2 formation, this central atom is bonded with two oxygen atoms, and their structure can be given as O=S=O. One sigma and one pi bond are formed for the bonding between the sulphur and two oxygen atoms. The atom will also accommodate one lone pair.

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Let us further break it down. The ground state of the sulphur consists of six electrons in the outermost shell, where the first two shells are also filled. There exist 4 electrons in the 3p portal and two paired electrons in the 3s orbital. Now, it should form four bonds (with oxygen) and thus requires 4 unpaired electrons. This leads to an excited state development in sulphur, where one 3px electron jumps to the 3d orbital. There will be only one unpaired electron in one 3d orbital and three in 3p orbitals when this happens. However, the electrons which form the sigma bonds and the lone pair will be at different energy levels. A stable state is obtained when the hybridisation of SO2 occurs.

At the time of sulphur dioxide hybridization, two 3p and one 3s orbital get hybridized. In total, there are three sp2 hybrid orbitals. Here, the two-hybrid orbitals have unpaired electrons, and one hybrid orbital will have the lone pair. Then, the unpaired electrons will form sigma bonds with the oxygen atoms. Meanwhile, the 3d and 3p orbitals remain the same, and they take part in the successful formation of pi bonds.

Adding, the hybridization of the oxygen atom in this compound is sp2.

Name of the Molecule

Sulphur Dioxide

Molecular Formula


Hybridization Type


Bond Angle



Bent or V-Shaped

SO2 or Sulfur Dioxide Molecular Geometry

We all know that the shape that minimizes the electronic repulsion pairs is adopted by the molecule to further form the structure. The SO2 molecular shape is similar to the molecular geometry of Carbon Dioxide (CO2). The bonding of SO2 without making assumptions can be shown below.

O === S === O

Now, if we want to check the correct SO2 molecular shape, then we should understand the number of electrons distributed between Sulphur and Oxygen and the positions. Sulphur has six electrons in the outer level, and the Oxygen has four of them while one electron is used for each bond. So, the total number of ten electrons in five pairs. Four pairs are needed to make bonds, so one pair remains alone. Then, the two double bonds use two pairs each and form as a single unit.

As the single lone pair is not counted in the shape's description, we can conclude that the SO2 molecular shape is either Bent or V-Shaped. So, the first perception of the original structure does not match with that of the original one.

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Electron Geometry Vs. Molecular Geometry

Even though there are many similarities between the electron and molecular geometry, there are some key differences. The most notable difference is that electron geometry can be associated with either one or more molecular shapes. It is based on the central structure of the atom of a molecule's electrons. At the same time, the molecular geometry is dependent on the other atoms, too, which are bonded to the free pairs of electrons or the central atom.

SO2 Lewis Structure

To form the Lewis structure of SO2, we need to arrange eight valence electrons on the Sulphur. We also need to calculate the formal charge of every atom as well. We know that both the Sulphur and Oxygen have six valence electrons each. Here, we have two Oxygen atoms, so the total number of valence electrons will be 18.

So, we will place the oxygens at outsides and Sulphur at the centre. Now, we put the electrons pair between the atoms to create bonds. Then, let us calculate the formal charges.

For Oxygen

  • Number of valence electrons are, 6

  • Number of bonds are, 2

  • Lone pairs are, 2

  • So, the Formal Charge (FC) = Number of valence electrons – Number of Bonds – 2 X (Number of lone pairs) = 6-2-(2×2) = 0

For Sulphur

  • Number of valence electron is, 6

  • Number of bonds are, 2

  • Lone pairs are, 2

  • So, Formal Charge (FC) = 6-2-(2×2) = 0

  • Now, we will form the structure by the octet completion with the most electronegative element O and place a double bond, a single lone pair with each Oxygen atom

  • Then, we will finish the structure by placing the valence electrons remaining on the central atom. Here we have four bond pairs and four lone pairs, so the total electrons used are (4+4) x 2 = 16. Hence, the number of valence electrons remained are 18-16 = 2. We will place these electrons on the Sulphur atom

  • So, the final Lewis structure of SO2 will result as follows

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FAQs (Frequently Asked Questions)

1. Explain the Sulfur Dioxide Bond Angle and Electron Geometry.


SO Bond Angle

SO₂ has a bond angle of 120 degrees. Using covalent bonds, one single atom of Sulphur is bonded with the two atoms of Oxygen. It also causes a repulsion of electron pairs to form an angle of 120 degrees.

SO2 Electron Geometry

The SO₂ electron geometry is formed in the trigonal planar shape. The three pairs of electron bonding will be arranged in the plane at the angle of 120-degree. As the one pair remains alone, two double pairs are bonded and thereby form a bent shape.

2. Is SO2 Polar or Nonpolar?

Ans: SO₂ is polar. Although the oxygen and sulphur atoms are both highly electronegative, oxygen is more electronegative than sulphur. So, the oxygen-sulfur bonds are slightly polar because the oxygen exerts more control over the covalent bond's electrons.

However, the molecules are necessarily not polar only because there are polar bonds present in them. These polar bonds make SO₂ polar because the molecule is also bent, same to H₂O, and is positioned with sulphur in the middle. Therefore, the molecule is not symmetrical entirely. The side with both oxygen atoms pointing toward is partially negative. The side with a sulfur atom has a partial positive charge, causing the molecule to have polarity.

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