MO Diagram, SO2 Lewis Structure, Hybridization, and Molecular Geometry

Have you ever wondered what generates the scent of burning matchsticks? The correct response is SO2!

SO2 is a very advantageous gas. In addition to its primary function, which is the generation of sulfuric acid, SO2 has various purposes in the chemical industry.

However, before reading through them, please read the following article. Because at the end, you will have a thorough understanding of the fundamentals of SO2 before moving on to the reactions.

So let’s begin!!

In Commonwealth English, sulphur dioxide is spelt as sulphur dioxide. This is an odourless and colourless gas.

In terms of its characteristics, the molar mass of SO2 is 64,066 g/mol. The melting point and boiling point are, respectively, -72°C and -10°C.

Now we will discuss essential concepts such as Lewis structure, molecular geometry, the MO Diagram, and SO2 hybridization.

SO2 Lewis Structure

Before diving into the lewis structure of SO2, let’s briefly explore the significance of lewis structure and the methods required to draw it.

The distribution of electrons around the atoms of a chemical is its Lewis structure.

This structure allows us to determine the type and amount of bonds that comprise the molecule.

Now let’s examine the process of drawing lewis structure:

Step 1 – The first and most crucial step is determining the total amount of valence electrons in the molecule. While doing so, be mindful of the + and – symbols. A ‘+’ signifies electron loss, whereas a ‘-‘ signifies electron gain.

The second step is to identify the core atom. The central atom is the atom with the maximum number of bonding sites.

The third stage is to create a skeleton structure with only single bonds.

After forming single bonds, the fourth step involves completing the octet of the atoms with the leftover electrons. Always start with the electronegative atoms and then proceed to the electropositive atoms.

Step 5: If double or triple bonds are required to satisfy the octet rule for all atoms, they must be formed.

Step 6 – Finally, it is essential to ensure that all atoms have the lowest feasible formal charge. Using the following methods, formal charge calculations can be performed:

Observe the Lewis structure of SO2 now.

In SO2, the valence electron of sulphur equals six.

And oxygen’s valence electrons equal six

The molecule contains 2 oxygen atoms, therefore = 6*2 = 12

So, total valence electrons = 18

After drawing the skeletal structure, it is evident that no atoms can complete their octet with single bonds. Thus, a double bond is necessary. Consequently, the amount of electrons utilised in double bonds = 8

Subtracting that from the total number of valence electrons, we are left with 10 electrons. We must position these remaining electrons around the atoms in accordance with the specifications.

This will eventually complete the atom’s octet. Oxygen has two lone pairs, while sulphur has one.

Lastly, remember to check the formal charge of each atom!

Next, we must learn about the hybridization of SO2.

SO2 Hybridization

Sp2 is the hybridization product of SO2

Now, hybridization of SO2 can be comprehended in two ways: the first is through theory, and the second is through formula application. I would recommend understanding the theory first, then proceeding to the formal.

A brief tip: when one s orbital combines with two p orbitals, Sp2 hybridization results in three equal s orbitals.

Similarly, the ground state electronic arrangement of SO2 is 1s2 2s2 2p6 3s2 3s4. When an electron is in an excited condition, it jumps from 3px to 3d orbital. Hence, we have 3p3.

Now, 3s2 and 3p3 combine to generate Sp2 hybridization, which consists of 3 analogous orbitals with 2 paired and 2 unpaired electrons.

Sulfur requires two unpaired electrons from the Sp2 hybridised orbitals in order to create two sigma bonds with oxygen. And the remaining two pairs of orbitals make up sulfur’s lone pair.

Are you curious about the two 3p electrons that were not involved in hybridization?

Specifically, one electron in the 3p orbital and another electron in the 3d orbital established the bonds between sulphur and oxygen. There is an image linked below for your convenience.

Now for the formula portion.

The formula for determining the hybridization of any substance is:

H = ½ [V+M-C+A]


H symbolises hybridization

V represents the number of valence electrons

M represents the number of monovalent atoms

C symbolises cationic charge

A illustrates anionic charge

Here, if H is 2, Sp hybridization occurs.

When H = 3, Sp2 hybridization occurs.

When H = 4, Sp3 hybridization occurs.

Similarly, H = 5, its hybridization with Sp4

And last, when H is six years old, Sp3d2 hybridization will occur.

Because oxygen is a divalent element, the number of valence electrons on the S atom in SO2 is six and the number of monovalent atoms is zero.

As it is a neutral molecule, both cationic and anionic charges are nil.

Thus, H = ½ [6+0-0+0]

H = ½ * 6

H = 3 Indicates hybridization with Sp2

I think the explanations of both ideas make SO2 hybridization apparent.

SO2 Molecular geometry

SO2’s molecular geometry is curved, having a bond angle of 120 degrees.

Using the provided chart, we can determine the molecular geometry of any chemical with ease.

Here, A represents the centre atom, X the atoms surrounding it, and E the lone pairs. SO2 is an AX2E-type molecule with 2 surrounding oxygen atoms and 1 sulphur atom pair.

However, SO2’s electron shape is trigonal planar. You must be curious about this novel term, correct? Let me clarify.

In establishing the shape, electron geometry differs from molecular geometry since it takes into account all electron pairs (including lone pairs). In contrast, molecular geometry solely concerns atoms.

In the absence of a lone pair, the geometries of all compounds are identical.

The shape of the SO2 molecule is seen in 3D below.

Now, let’s examine the final topic of this tutorial, the SO2 molecular orbital diagram.

SO2 Molecular Orbital Diagram

The SO2 molecular orbital diagram is shown below.

A molecular orbital diagram illustrates how the atomic orbitals of two distinct atoms can combine to form a new orbital.

This provides additional assistance in determining the bond order, bond length, and bond strength of any compound.

In this MO, the AO of sulphur, which is located on the left, combines with the AO of oxygen, which is located on the right.

We may observe that the orbitals contain 18 electrons according to the proper rule.

In addition to bonding orbitals, non-bonding orbitals are also present. Additionally, the antibonding orbitals of SO2 are vacant.

This concludes the discussion of the SO2 molecular orbital diagram.

Polarity of

The SO2 molecule is characterised as a polar molecule due to the unequal distribution of charge across its atoms.

As sulphur is more electronegative than oxygen, it attracts the charge and acquires a partial negative charge. hence, polarisation exists.

Additionally, you can consult the article on the polarity of SO2.

Now, let’s also discuss its preparation techniques.

SO2 Preparation

There are multiple methods for producing SO2. I am dissecting each strategy to make it simple to comprehend!

Method 1 – The primary source of SO2 is the generation of sulfuric acid via the contact process. Among all other methods for producing SO2, this one is the most prevalent.

(Because Chemistry has a great deal to do with history, here is an interesting historical fact! In 1979, the United States produced sulfuric acid using 23.6 million tonnes of SO2!

Method 2 – Sulfur or products containing sulphur can be burned to produce SO2.

S + O2 ——-> SO2

2 H2S + 3O2 ——–> 2H2O + 2SO2

Method 3 — The roasting of pyrite, sphalerite, and cinnabar can also produce SO2 ( sulphide ores).

Method 4 produces SO2 as a byproduct of calcium silicate cement production.

2 CaSO4 + 2SiO2 + C ———> 2CaSiO3 + 2SO2 + CO2

Method 5 – In the laboratory, heated concentrated sulfuric acid reacts with copper turnings to produce SO2.

Cu + 2H2SO4 ——–> CuSO4 + SO2 + 2H2O

Method 6 – Natural disasters such as volcanic eruptions can generate a substantial amount of SO2.

Now we will discuss the Lewis structure of SO2!


This page explains pretty much everything you need to know about SO2.

Before studying the SO2 reactions and equations, read this page to clarify your understanding of SO2’s Lewis structure, geometry, hybridization, and MO diagram.

If you have any questions, you may contact me at any time. Enjoy your reading!

Read more: Polar or nonpolar, is SO2? 

Misha Khatri
Misha Khatri is an emeritus professor in the University of Notre Dame's Department of Chemistry and Biochemistry. He graduated from Northern Illinois University with a BSc in Chemistry and Mathematics and a PhD in Physical Analytical Chemistry from the University of Utah.


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