SO2 ionic or covalent: Everything about SO2’s bonding

SO2 ionic or covalent: Everything about SO2’s bonding SO2 is a covalent compound. Covalently bonded compounds are formed when atoms share electrons to complete an octet. Here, when two atoms with similar electronegativity are bonded, a slight difference in their electronegativity leads to the sharing of bound electrons.

We are going to discuss about Lewis structure of SO2, resonance structures, it’s geometry and hybridization according to VSPER theory and some of it’s properties related to it’s bonding like dipole moment and acidic or basic nature of SO2.

Note: If you are not looking for detail and searching for direct answers you can check the “Conclusion”.

SO2 ionic or covalent compound

Condition of Sulphur in ground state:

Sulphur belongs to VI A group of periodic table. It is the second element of it’s group and belongs to 3rd period (the group starts from 2nd period, as you can see below). So according to it’s position in periodic table, sulphur has 3 shells K, L and M and it has 16 electrons. The valence shell contains 6 electrons. The electronic configuration of sulphur will be 1s², 2s², 2p⁶, 3s², 3p⁴.

periodic table

Condition of Oxygen in ground state:

Like sulphur oxygen also belongs to VI A group of periodic table. It is the first element of its group so it’s in 2nd period (as the group starts from 2nd period). Sulphur has 2 shells K and L. It has 8 electrons in total and 6 valence electrons. It’s electronic configuration is 1s², 2s², 2p⁴.

Fun fact: During volcanic eruption, SO2 gas is released in large quantities.

Lewis structure of SO2:

What is Lewis structure?

Before getting into the Lewis structure of SO2. Let’s see what Lewis structure actually is. Lewis structure which is also known as electron dot structure or Lewis dot structure is a diagrammatic representation of the bonds formed between the elements of a molecule. These structures are drawn in a manner to make the formal charges 0 for all the elements of the molecule.

If the formal charges are not zero we try to make them zero by changing the bonds and by moving electrons. In these cases we get more than 1 structure for a single molecule. These structures are called resonance structures.

Rules for drawing Lewis structure:

For drawing the lewis structure we have to follow some steps.

1.Draw the less electronegative element in center. More electronegative elements will be on sides.

2.Draw the valence electrons (electrons of outermost shell) of all elements.

3.Start filling the valence orbits to get 8 electrons by drawing bonds.

4.Check the formal charges or oxidation number.

This is the overview of the method for drawing the lewis structure.

1st resonance structure:

Oxygen is more electronegative than sulphur so we have placed it on sides. Sulphur has electronegativity of 2.58 while oxygen has 3.44. Now we have to start making bonds. As both the elements are non metals and have 6 valence electrons so they will form covalent bonds.

1.Sulphur will make double covalent bond with 1 oxygen atom. In this way both the atoms will get 8 electrons.

2.But we have another oxygen left and it needs 2 electrons so sulphur can donate it’s 1 lone pair to oxygen atom and forms a coordinate covalent bond.

3.Our structure is complete and satisfy octet rule as well. Let’s look at the formal charges of these atoms.

Formal charge check:

But how will you find the formal charges? There is a formula for that, “valence electrons – (non bonded electrons + bonds formed)”.

For sulphur:

Sulphur had 6 valence electrons and now sulphur has 2 non bonded electrons and 3 bonds with 2 oxygen atoms. Let’s put these values in our formula
6 – (2+3) = +1

For Double bonded oxygen:

Oxygen also had 6 valence electrons and now it has 4 non bonded electrons and 2 bonds with sulphur so,
6 – (4+2) = 0

For 2nd oxygen:

It also had 6 valence electrons. After bonding it has 6 non bonded electrons and 1 bond with sulphur so,
6 – (6+1) = -1

2nd resonance structure:

The second structure is same as the first one we just flip the bonds of oxygen atoms.

Formal charge check:

For Sulphur:

The situation is same as before for the sulphur atom.
6 – (2+3) = +1

For Double bonded oxygen:

It had 6 valence electrons and now it has 4 no bonded electrons. 2 bonds are formed with sulphur.
6 – (4+2) = 0

For 2nd oxygen atom:

It has 6 non bonded electrons and 1 bond with sulphur so,
6 – (6+1) = -1

As we can see by changing the position of bonds the charges have changed their position as well. But our molecule is still not neutral.

3rd resonance structure:

We all know that sulphur has a d orbital (since it has 3 shells). It has the capacity to hold more electrons than 8. So if we remove the coordinate covalent bond and make a double covalent bond our molecule will become neutral.

Formal charge check:

For sulphur:

Now it has 2 non bonded electrons and 4 bonds so,
6 – (2+4) = 0

For oxygen atoms:

Both oxygen atoms have 4 non bonded electrons and 2 bonds with sulphur so,
6 – (4+2) = 0

You can check the following video regarding lewis structure of SO2.

Cause of the resonance:

You might be a little confused that which structure is actually correct? Practically we have found that the real structure is some what between these structures. For understanding we can say that it has 2 double covalent and half coordinate covalent bond.

The structures are not continuously flipping but there is only one intermediate structure. So the resonance structures are represented in the following way with the help of double sided arrow.

Reason for intermediate structure:

But why is it an intermediate structure? It is because of delocalized pi bond. The pi bonds are weak so they can delocalize themselves and we see an intermediate strange structure that is difficult to understand. But it’s not difficult for the nature to create it.

Geometry of SO2 according to VSEPR theory:

geometry of so2

Valence shell electron pair repulsion (VSEPR) theory gives the explanation about the geometry of a molecule. It’s bond angle and about it’s polarity.

According to this theory the electron pairs repel each other to a position of least repulsion. Due to this reason some molecules are straight and some are bent.

There is another thing called hybridization. It happens during bond formation. The orbitals have different energies so they degrade themselves and make same number of identical orbitals (same shape and energy).

Now let’s look to the molecule of SO2. In SO2 sulphur and oxygen atoms, all are sp2 hybridized (1 s and 2 p orbitals are hybridized). So the molecule of SO2 is not linear it’s bent. The bond angle is 120° and it has trigonal geometry. This geometry is the reason for SO2’s polarity. Since this molecule is not linear so the charges don’t cancel each other’s effect and SO2 becomes a polar molecule.

Pi and Sigma bonds of SO2:

You may be wondering how many pi and sigma bonds does SO2 have? Well SO2 has 2 pi and 2 sigma bonds. This is according to the third resonance structure. In one double covalent bond there is always 1 sigma and 1 pi bond present. SO2 has 2 double covalent bonds. 1 with each oxygen atom so it has 2 pi and 2 sigma bonds.

Fun fact: Sulphur dioxide causes acid rain. It reacts with water vapors of air and form H2SO3 acid which comes down with rain. That’s why SO2 cause pollution.

Is SO2 acidic or basic?

SO2 is acidic. If you dissolve SO2 in water it will react with water molecules to give sulphurous acid (H2SO3). If you are thinking that will SO2 dissolve in water? So, yeah definitely SO2 is a polar molecule so it can easily dissolve in water. Unlike sulphuric acid H2SO3 is a weak acid.

SO2 + H2O → H2SO3

Chemistry of SO2

Is SO2 reducing agent or oxidizing agent?

Sulphur dioxide can be categorized into both types. Yes, SO2 can act as a reducing agent as well as a oxidizing agent. The reason behind this behavior is that sulphur has a +4 oxidation state in SO2 molecule. So it can either oxidize itself to +6 oxidation state (act as a reducing agent).


In the following reactions sulphur has gained +6 oxidation state.

2SO2 + O2 →2SO3

SO2 + Cl2 → SO2Cl2

Or it can reduce itself to -2 oxidation state (act as an oxidizing agent).


SO2 + 3H2 → H2S + 2H2O
In this reaction sulphur has -2 oxidation state in H2S

Fun fact: SO2 has temporary bleaching effect. It is because it acts as reducing agent and remove oxygen from the colored compounds. The removal of oxygen makes the substance colorless. However, soon atmospheric oxygen takes it’s place and color reappears.

Dipole moment of SO2:

You might be wondering about the dipole moment of SO2. As it is mentioned above that in SO2 there is a difference of electronegativity between sulphur and oxygen atoms and it is also a polar molecule so it should have a dipole moment. The answer to this question is yes, sulphur dioxide has a dipole moment and it has the value of 1.61 Debye.


1.SO2 or sulphur dioxide is colorless gas with a pungent smell.

2.It is a covalently bonded molecule. SO2 contains double covalent bond with one oxygen atom and a coordinate covalent bond with the other one.

3.Sulphur dioxide has sp2 hybridization in both sulphur and oxygen atoms.

4.It contains 2 sigma and 2 pi bonds

5.SO2 is not linear it has bent structure and has trigonal geometry. It has a bond angle of 120°. Due to this structure of SO2 it is a polar molecule because the charges can’t cancel the effect of each other.

6.SO2 is acidic in nature. The reason behind this is that SO2 reacts with water to form H2SO3 or sulphurous acid which is a weak acid.

7.This molecule act as oxidizing as well as reducing agent because it has +4 oxidation state. So it can change its oxidation state to a higher as well as to a lower level.

8.Since the molecule is polar so it has a dipole moment of 1.61 Debye.

So now you know all about SO2. Whether it is ionic or covalent, polar or non polar, acidic or basic. You now know the answers and the reasons for all that as well.

Read also:
N2O Lewis Structure
H2O Lewis Structure
Write the structure of 2 methyl cyclohexane?
Types Of Chemical Reactions

Sulfur dioxide molecule contains one sulfur atom or two oxygen atoms. We would construct the lewis structure of the SO2 molecule by following VSEPR theory rules or considering stability of the intermediate structures. After obtaining the lewis structure of the SO2, we may determine the hybridization of the atoms.

Sulfur dioxide SO2

Sulfur dioxide is the the colourless inorganic gas or also the toxic gas. this gives the weak acid solution if dissolves in the water. This gas is the produced due to the combustion of the petroleum fuel in the automobiles or industrial factories.

Lewis structure of the SO2

There are the two double bonds between sulfur atom or oxygen atoms in the SO molecule. Also, the lone pair exists on the sulfur atom or each oxygen atom has two lone pairs in the SO2 lewis structure.

Hybridization of the SO2

All atoms have sp2 hybridization. Each oxygen atom has one sigma bond or two lone pairs. Therefore, oxygen atoms’ hybridization should be sp2. for the sulfur atom, there are the two sigma bonds or one lone pair to the make hybridization sp2. Simple method to the determine the hybridization of the atoms in the covalent compounds.

Apply VSEPR theory - Steps of the drawing lewis structure of the SO2

Following steps are the used to the draw the lewis structure of the SO2. Each step is the explained in the detail in the next sections. If you are the beginner to the lewis structure drawing, follow these sections slowly or properly to the understand this completely. Look the figures to the understand each step.

  1. Find total number of the electrons of the the valance shells of the sulfur or oxygen atoms

  2. Total electrons pairs

  3. Center atom selection

  4. Put lone pairs on the atoms

  5. Check the stability or minimize charges on the atoms by converting lone pairs to the bonds until most stable structure is the obtained.

Total number of the electrons of the valance shells of the ethene

Both sulfur or oxygen belongs to the group VIA elements series. Therefore, they have six electrons in the their valence shell. to the find number of the valence electron, these valence electrons of the each element should be multiplied with the their respective number of the atoms in the molecule. Below, this step are the done.

• Total valence electrons given by two oxygen atoms = 6 * 2 = 12

• Total valence electrons given by sulfur atom = 6 * 1 = 6

There are the no charges in the SO2 molecule. Therefore, no addition or reduction of the valence electrons due to the charges.

• Total valence electrons = 12 + 6 = 18

Total valence electrons pairs

Total valance electrons pairs = σ bonds + π bonds + lone pairs at the valence shells. Total electron pairs are the determined by dividing the number total valence electrons by two. For, SO2 molecule, Total number of the pairs of the electrons are the 9.

Center atom or sketch of the ethene molecule

There are the few requirements to the be the center atom. Having the high valence is the the main requirement to the be the center atom. for the SO2 molecule, sulfur has the highest valence than or oxygen.

Mark lone pairs on the atoms

After drawing the sketch, we should start to the mark lone pairs on the atoms. In the drawn sketch, there are the two bonds. between atoms.

• There are the already two S-O bonds in the the above sketch. Now, there are the just seven (9-2 = 7) valence electrons pairs are the remaining to the draw (as mark lone pairs) the rest of the structure.

• First, mark remaining valence electrons pair as the lone pairs on the oxygen atoms (outside atoms). Six valence electron pairs are the marked on the two oxygen atoms. Now, there are the still one valence electron pair is the remaining. this is the marked on the sulfur atom as the lone pair.

• Now, all valence electron pairs are the marked as bonds or lone pairs in the sketch.

Charges on the atoms

Charges on the atoms are the important to the find the most stable structure. Therefore, we need to the find the most stable structure to the obtain lewis structure. Therefore, we should try to the find charges if there are.

After, marking electron pairs on the atoms, we should mark charges of the each atom. Each oxygen atoms would take the -1 charge or sulfur atom take the +2 charge. Because SO2 is the neutral molecule, overall charge of the molecule should be zero. The overall charge of the molecule is, (-1) * 2 + (+2) = 0.

Stability of the structure or minimize charges on the atoms by converting lone pairs to the bonds

When there are the positive or negative charges on the lot of the atoms or higher charges (like +2, +3, -2, -3) on the atoms in the an ion or molecule, this structure is the not stable. Therefore, We should try to the reduce charges on the atoms if this is the possible. in the thee above structure, there are the charges on the oxygen atoms or sulfur atom. Now, we are they going to the reduce charges on the these atoms as below.

• Now, we should try to the minimize charges by converting the lone pair or pairs to the bond. So convert the lone pair on the oxygen atom to the make the new S-O bond with the sulfur atom as the following figure.

• Now there is the double bond between one oxygen atom or sulfur atom. You may see, charges are the reduced now in the new structure.

• Because, there are the still charges on the atoms, we may try to the convert the lone pair to the bond. So, convert the lone pair on the other oxygen atom to the make the bond with the sulfur atom. with the that, there are the no charges on the sulfur or oxygen atoms.

• Therfore, this structure should be the lewis structure of the SO2

How many lone pairs sulfur has in the SO2

There is the just one lone pair on the valence shell of the sulfur atom.

SO2 lewis structure lone pairs

There are the lone pairs on the all atoms in the SO2. Sulfur atom has one lone pair or each oxygen atom has two lone pairs. Therefore, there are the total of the five lone pairs on the last shells of the each atom in the SO2.

What are the other similar lewis structures of the SO2?

If we consider the shape of the SO2, water, nitrogen dioxide, hydrogen sulfide, ozone have similar shape, bent. Also, if number of the sigma bonds are the is the considered, water, nitrogen dioxide, hydrogen sulfide, sulfur dioxide all have two sigma bonds. Both SO2 or ozone has one lone pair on the center atom.

Are there similarities in the SO2 or NO2 lewis structures?

Actually, this question is the weird one. Rather than discussing similarities, it’s good to the discuss their differences. in the NO2 lewis structure, there is the an unpaired electron on the nitrogen atom.

What are the similarities or differences in the SO2 or SO3 lewis structures?

• Around sulfur atom, summation of the lone pair or sigma bonds is the three in the both SO2 or SO3. Therefore, sulfur atom has sp2 hybridization.

• But, shapes around sulfur atom in the SO2 or SO3 are the different. in the SO2, shape around sulfur atom is the bent. But in the SO3, shape is the trigonal planar.

so2 ionic or covalent

So 2 is covalent.

so2 lewis structure

SO2 is a very beneficial gas. In addition to its main use, the production of sulfuric acid, SO2 has multiple functions in this chemical industry.

But before going through them, pause a bit and read this article. Ultimately, you’ll have a deep knowledge of all the basics of SO2 you need to know before proceeding with the reaction.

Let’s begin!

Sulfur dioxide is spelled as sulfur dioxide in Commonwealth English. This is a colorless gas with a pungent odor.

In terms of its properties, the molar mass of SO2 is 64.066 g / mol. Melting points and boiling points are -72 ° C and -10 ° C, respectively.

Now let’s move on to basic concepts such as Lewis structures, molecular structures, MO diagrams, and SO2 hybrids.

SO2 Lewis structure
Before diving directly into the Lewis structure of SO2, let’s briefly explain the importance of the Lewis structure and the procedure for drawing it.

The Lewis structural formula is the distribution of electrons around the atoms of a compound.

This structure helps to know the types of bonds that form the compound and the number of bonds.

Now let’s see how to draw a Lewis structure.

Step 1: Knowing the total number of valence electrons in a molecule is the first and most important step. Pay attention to the + and – symbols. The “+” sign means to lose an electron, and the “-” means to gain.

Step 2: The next step is to find the central atom. The atom with the largest number of binding sites is the central atom.

Step 3: The third step is to create a single bond only skeleton structure.

Step 4: Next, after the formation of the single bond, the remaining electrons complete the octet of the atom. Always start with an electronegative atom and move to an electropositive atom.

Step 5: Double or triple bonds must be given if necessary to satisfy the octet rule of all atoms.

Step 6: Finally, it is important to check if the formal charges of all atoms are as low as possible. Formal pricing can be done using:

In SO2, the valence electron of sulfur = 6

And the valence electron of oxygen = 6

Since the compound has two oxygen atoms, = 6 * 2 = 12

Therefore, valence electron = 18

After drawing the skeletal structure, it turns out that no atom can fill the octet with a single bond. Therefore, a double bond is required. Therefore, the number of electrons used in the double bond = 8

Subtracting it from the total valence electron gives 10 electrons remaining. These remaining electrons must be placed around the atom according to requirements.

This finally completes the atomic octet. Oxygen has two lone pairs of electrons, and sulfur has one lone pair of electrons.

Finally, don’t forget to check the formal charges of all atoms!

so2 hybridization structure

For sulfur dioxide (SO2), the type of hybridization that occurs is sp2. To explain this, let’s first look at the sulfur atom. This is the SO2 hybrid orbital of the central atom. During SO2 formation, this central atom is bonded to two oxygen atoms, and their structure can be given as O = S = O.

oxidation number of s in so2

The oxidation number of sulfur in SO2 is +4. To find this oxidation number, it is important to know that the sum of the oxidation numbers of atoms in neutral compounds must be zero. In the compound sulfur dioxide (SO2), the oxidation number of oxygen is -2.

To find the sulfur oxidation number, just use the formula SO2 and write the oxidation numbers in the form S = (x) and O2 = 2 (-2) = -4. Using the rule and adding the oxidation numbers in the compound, the equation becomes x + (- 4) = 0. Solving for x, it is evident that the oxidation number for sulfur is +4.

In chemical compounds, the oxidation number of an atom refers to the charge that atoms have if the compound is made up of only ions. When writing formulas or compound reactions, rules are used to assign oxidation numbers.

so3 ionic or covalent

So3 is covalent.

so2 bond

So 2 has polar bond.

so2 covalent bond structure

Bond Type: Sulfur dioxide is a covalent bonding process, since sulfur and oxygen are both non-metals. The sulfur is in the center surrounded by 2 oxygen atoms. In this situation, as illustrated below, sulfur dioxide is a resonant structure and can be expressed in three different forms.

so2 shape

SO2 has a bent shape.

sulfur dioxide polarity

Some molecules contain only nonpolar bonds - for example, methane, CH4. Such molecules are nonpolar molecules. Other molecules contain polar bonds, that is, bonds between atoms whose electronegativities differ by more than 0.4 units. Whether these latter molecules are polar or nonpolar depends on the spatial arrangement of these bonds and the resulting geometry of the molecules. If we imagine the geometry of a molecule and show its polar bonds with an arrow pointing to the most electronegative atom.

why is so2 bent

In sulfur dioxide, as well as the two double bonds, there is also an isolated pair on sulfur. To minimize repulsions, the double bonds and the isolated pair move apart as far as possible, and so the molecule is bent.

so2 dipole

SO2 has an asymmetric charge distribution, resulting in a net dipole moment (yellow arrow) relative to CO2 (left). Polarity determines many physical and chemical properties of molecules and how molecules interact with other molecules.

why does so2 have two double bonds?

Externally, Sulfur has six electrons and Oxygen has four of which one electron is used for each bond. So total number of ten electrons in five pairs. To make links, you need four pairs, so one pair remains alone. The two double bonds each use two pairs and form a single unit.

how many lone pairs does sulfur have

In sulphur, we can see that the sulfur atom shares a bond pair and has three lone pairs and has a total of six valence electrons.

so2 lewis structure angle

SO2 has a bond angle of 120 degree.

SO2 formal charge

Thus, neither negative nor positive charge is present on the S atom. Therefore, the formal charge on the S atom in SO2 is zero.

SO2 vsepr

The molecular geometry of SO2 is considered to be V-shaped or curved. Alternatively, the electronic geometry of sulfur dioxide has the shape of a trigonal plane. The three bond electron pairs form an angle of 119 degree.

sulfur covalent bonds

Sulfur can use its 2 unpaired electrons to form 2 covalent bonds plus the 4 electrons of its 2 isolated pairs to give a total of 8 electrons. Now sulfur has 6 unpaired electrons which means it can form 6 covalent bonds to give a total of 12 electrons around its valence shell.

Frequently Asked Questions (FAQ’s)

Q: Does SO2 have dative bonds?

The sulfur and oxygen atoms have 6 valence electrons and each lacks 2 electrons to complete its octet. The sulfur atom and the oxygen atom each share two electrons, thus forming a double bond between them. The sulfur atom still has 4 unshared electrons, that is, two lone pairs to donate.

Q: What types of bonds are present in SO2?

The sulfur dioxide molecule contains 2σ, 2π bonds and a single pair of electrons. The S atom contains 6 valence electrons of which it shares 2 electrons with 2 O atoms to form 2 sigma bonds. It also shares 2 electrons with 2 O atoms to form bonds.

Q: What is the strongest intermolecular force in SO2?

SO2 is a polar molecule. In general, dipole-dipole forces are stronger than LDF forces.

Q: Does KCN contain both ionic and covalent bonds?

The bond between K + and CN- is ionic, while the bond within CN- is a covalent bond. Therefore, both ionic and covalent bonds are present in the KCN.

Q: Is PCl3 a covalent bond or an ionic bond?

PCl3 is distorted due to the presence of lone pairs of electrons. PCl3 is a covalent molecule because it contains three covalent bonds formed by evenly sharing electrons between phosphorus and chlorine atoms.

Q: Is Al2O3 a covalent bond or an ionic bond?

Aluminum oxide (Al2O3) is not an ionic compound. It is a covalent compound.

Q: Is iodine an ionic compound?

Iodine is included in Group 17 of the Periodic Table. That means it is non-metal. Metals react with non-metals to form ionic compounds. Similarly, potassium atoms move electrons to iodine atoms to form potassium and iodide ions.


SO2 is a very beneficial gas. In addition to its main use, the production of sulfuric acid. SO2 has multiple functions in this chemical industry.