Best Overview: Is SO2 Polar or Nonpolar - Science Education and Tutorials

Sulfur and oxygen compounds are very different and unique in nature. Sulfur dioxide has the chemical formula SO2. All atoms belong to the non-metal oxygen family group in the periodic table and possess a high electronegativity value. Students used to ask “Is SO2 polar or nonpolar?”, “SO2 Lewis Structure”, “SO2 molecular geometry”, “SO2 bond angle”, and “SO2 polarity”. In this blog post, we are going to discuss the polarity of SO2 in a detailed manner.

SO2 is commonly appearing at ordinary temperatures and pressures, it exists as a colorless gas with a fumy texture. SO2 contains one sulfur atom and two oxygen atoms. Sulfur dioxide (SO2) is corrosive to biological tissue and metals, and it can produce corrosive acid when reacted with water. The sulfur atom stays the center of the molecule and the remaining two oxygen atoms in the two terminals of the molecule. “Is SO2 polar or nonpolar?”, to answer this question, we need a detailed analysis of the polarity of the SO2 molecule.

Because of the bend V- type form of sulfur dioxide(SO2). Oxygen has atomic number 16 in the modern periodic table and six outermost valence shell electrons. It comes under the oxygen family group. Similarly, Sulfur has atomic numbers 16 and six outermost valence shell electrons. Total electron counting on sulfur and oxygen atoms, only two electrons are required to attain the octet stability.

SO2 molecule is formed by elements of the oxygen family group in the periodic table. When SO2 is exposed to air, it absorbs water quickly and produces acid with white vapors that have a distinct odor and are toxic to breathe. Sulfur dioxide (SO2) can generate sulfuric acid when it reacts with water and this induces the formation of acid rain.

Is SO2 polar or nonpolar, then? SO2 (Sulfur Dioxide) is polar due to its bent geometrical shape caused by the presence of a lone pair on the sulfur atom. Second, the difference in electronegativity between sulfur and oxygen atoms causes the S-O bonds to become polar, causing the entire molecule to become polar as well, resulting in a net dipole moment of the SO2 molecule is 1.62D.

Table of Contents

Preparation of SO2

Sulfur dioxide(SO2) is a fumy colorless gas with a strong intense odor. It is created primarily through the combustion of sulfur. It is the heterogeneous reaction, sulfur in the solid phase and oxygen in the gas phase. Initially, sulfur reacted with oxygen gas in the combustion reaction formed sulfur dioxide(SO2). This reaction is a combustion reaction.

. The chemical thermodynamic equation of the sulfur combustion reaction is shown below.

S + O2 —-combustion——> SO2, ΔH(enthalpy) = −297 kJ/mol
Preparation of sulfur dioxide(SO2)

SO2 Molar Mass Calculation

SO2 has a molecular mass of 64.066 g/mol, which may be computed as follows.

Mol mass of SO2 = 1 * 32 (atomic mass of S) + 2 * 16 (atomic mass of O) = 64.066 g·mol−1.
SO2 molar mass calculation

The chemical composition of the Sulfur dioxide(SO2) molecule is 2 oxygen atoms and 1 sulfur atom in the middle.

Key Points To Consider When Determining The Polarity of SO2 Molecule

When attempting to determine the polarity of SO2 molecule, a three-step procedure can be used. The first stage is to sketch the SO2 molecule’s Lewis structure; the second step is to determine the SO2 molecule’s geometry; and the final step is to determine the SO2 molecule’s bond polarities (dipole moment) and add them together.

Drawing the SO2 Lewis structure is a method of representing a molecule using a diagram that shows the number of valence electrons and bond electron pairs in the SO2 molecule. The geometry of the SO2 molecule can then be determined using the Valence Shell Electron Pair Repulsion Theory (VSEPR Theory), which stipulates that molecules will adopt an SO2 geometrical formation that the electrons have from one another.

Finally, you must calculate the S-O bond’s strength by adding their bond polarities (dipole moment properties of SO2 molecule). The sulfur-oxygen bonds in sulfur dioxide(SO2), for example, are polarised toward the more electronegative oxygen, and because both bonds have the same magnitude, their sum is non zero due to lone pair of SO2 molecule, and the SO2 molecule is categorized as a polar.

The molecule of sulfur dioxide is angled at 119 degrees and has a difference in electronegativity value of sulfur and oxygen atom, with sulfur’s pull being lower than that of oxygen. As a result, a persistent dipole moment exists. The unequal distribution of negative and positive charges causes the dipole moment.

SO2 Lewis Structure: Is SO2 polar or nonpolar?

The middle core atom is sulfur, which is flanked by two oxygen atoms. Sulfur contains six outermost valence electrons, which means it contains six electrons in its outermost shell, whereas oxygen has six outermost electrons. An oxygen atom is required two electrons to complete the octet of oxygen atoms. If you want to know about the octet rule in oxygen, please see in our previous post.

As a result of this, both two oxygen atoms form covalent bonds with the sulfur atom, leaving the sulfur atom with one lone pair. The bond pairs of the S-O double bond are repelled by the one lone pair on the sulfur atom. According to VSEPR theory, electronic repulsion causes the molecule’s shape to bend (V-shape), similar to that of the water molecule.

The lone pair forces both two S-O bonds downward, resulting in the bent V-type form of the SO2 molecule. Because they generate electrical repulsion among the SO2 molecule, lone pair on sulfur atom have deformed shapes of the SO2 molecule.

Electronegative difference calculation SO2:

When it comes to the electronegativity value of the SO2 molecule, oxygen has an electronegativity value of 3.44, while sulfur has an electronegativity of 2.58. The electronegativity difference can be calculated by the following method.

Electronegativity value of oxygen = 3.44
Electronegativity value of sulfur = 2.58
Difference of electronegativity value between sulfur and oxygen = 3.44 – 2.58=0.86
Electronegativity difference calculation of SO2 molecule

The S-O bond of the SO2 molecule becomes polar in nature due to this difference in electronegativity values of sulfur and oxygen. “The power with which an atom can attract bound electron pairs towards its side is known as the electronegativity of the atom.”

As a result of this, the dipole moment of the S-O bond is non zero, and the dipoles of both S-O bonds are not negated due to the V-shaped structure. The total dipole moment of the SO2 molecule is calculated to be 1.62D. Sulfur atoms receive a partial positive charge on it, while oxygen atoms receive a partial negative charge on it.

SO2 molecule’s electron dot structure is also known as SO2 Lewis structure. It determines the number of outermost valence electrons and the electrons involved in the formation of the SO2 molecule’s bonds. When discussing the Lewis structure of the SO2 molecule, it is necessary to understand the outermost valence electrons of SO2.

Sulfur is the middle element of the molecule, with 6 electrons in its outermost valence electron shell, while oxygen atom is the outermost valence electron shell, with 6 electrons and two electrons missing in the shell to complete its octet.

As a result of this above explanation, the SO2 molecule contains a total of 18 valence electrons. The two oxygen atoms establish covalent connections with the sulfur atom, leaving the sulfur atom with one lone pair on it.

The lone pair of sulfur cause repulsion with S-O bond pairs, causing the S-O bonds to face downward force and the shape of the SO2 molecules to bend like that of the H2O (water) molecule. The O-S-O bond has a bond angle of roughly 119 degrees. S-O bond has a bond length of 143 pm (picometer).

To sketch the SO2 Lewis structure by following these instructions:

Step-1: Determine the total number of outermost valence shell electrons in the SO2 molecule. The first step is to figure out how many outermost valence shell electrons there are in the SO2 Lewis structure. A valence electron is one of an atom’s outermost shell electrons. In the SO2 Lewis diagram, it is represented by dots. The central sulfur atom of the SO2 molecule can be represented as follows

Look for the periodic group of each atom in SO2 to determine its valence electron. Sulfur and oxygen are both members of the oxygen family, which is the 16th group in the periodic table. Both oxygen and sulfur have six valence electrons in their outermost shell.

Because sulfur and oxygen belong to the oxygen family group in the periodic table, their valence electrons are six.

Total outermost valence shell electron of oxygen atom in SO2 = 6
Total outermost valence shell electron of Sulfur atom in SO2= 6
The SO2 molecule has one central sulfur atom and two oxygen atoms. Then the total outermost valence shell electrons can be calculated as follows
∴ Total outermost valence shell electrons available for SO2 Lewis structure( dot structure) = 6 + 6*2 = 18 valence electrons in SO2
calculation of total valence electron of SO2 molecule

Step-2: Locate the atom with the least electronegative charge and place it in the center of the SO2 molecular geometry. In this phase, we’ll select the least electronegative atom in the SO2 molecule to place in the SO2 Lewis structure diagram’s center. In the periodic table, the electronegativity value increases in order from left to right and decreases in order from top to bottom in periodic groups.

As a result, oxygen is the first atom in the oxygen family group in the periodic table. Sulfur comes second in the oxygen family group. A sulfur atom has a lower electronegative value than an oxygen atom. Furthermore, because the oxygen atom is the most electronegative element in the SO2 molecular structure, it can never be the central atom in the SO2 Lewis structure diagram. As a result of this, place sulfur at the center of the SO2 Lewis structure, with oxygen atoms uniformly around it the V shape structure.

Step-3: Use two double bonds (S-O) to connect the outside and core atoms in the SO2 molecule. Connect all outside atoms (oxygen) to the core central atom (sulfur) with two double bonds in this stage.

Count how many outermost valence shell electrons we’ve used so far in the SO2 structure. Because each Sulfur atom is connected to an oxygen atom by two double (S-O) bonds, each connection contains four electrons. Those are called double bond pairs.

So, from the total of 18 valence electrons available for the SO2 Lewis structure, we employed 8 electrons for two double (S-O) bonds in the SO2 molecule. There are still 10 valence electrons left in the SO2 molecule. Where do we need to place them in SO2 molecular geometry?

Step-4: Starting with the outer two oxygen atoms in the SO2 molecule, place the remaining valence electrons. We always start inserting valence electrons from the exterior atom first in the SO2 Lewis structure diagram. As a result, first, wrap around the leftover valence electrons on each oxygen atom.

To complete its octet, oxygen requires 8 electrons in its outermost valence shell. With the help of a double bond, each oxygen already shares four electrons. Put 4 electrons around each oxygen atom and you’re done with the oxygen in the SO2 molecule.

In the SO2 molecule structure above, we’ve put 8 electrons around the oxygen atoms, represented by a dot. As all oxygen atoms have 8 electrons in their outermost valence shell, each oxygen atom comfortably completes its octet stability in the SO2 molecule.

Using the SO2 Lewis structure, count how many outermost valence shell electrons have been consumed so far. In the SO2 molecular structure, 16 electrons are represented as dot structure, whereas two double bonds each contain 4 electrons. As an outcome of the calculation, the outermost valence shell electrons are 8 + 8 = 16.

So far, we’ve used 16 of the total 18 outermost valence shell electrons available for the SO2 Lewis structure. But now the question is, “How to fix the remaining four valence electrons?”. We also have two valence electrons to spare in the SO2 molecule.

Step-5: Complete central sulfur atom octet and use covalent bond if necessary. In the SO2 Lewis structure, Sulfur is the central atom and it is connected with two double bonds (S-O) to the oxygen atoms. It means it already sharing 8 electrons with the help of 2 double bonds.

So, sulfur is obeying the rule of the octet as 8 electrons around it. Place the two remaining valence electrons around the sulfur center atom, which is acting as an octet stabilization in this case.

What are SO2 electron and molecular geometry?

SO2 has a V-shaped bent molecular geometry and water like electron geometry, according to the VSEPR theory. Because the core central atom, sulfur, has two S-O bonds with the surrounding two oxygen atoms. In the same plane, the O-S-O bond forms a 119-degree angle. Because two oxygen atoms are in the same plane, they form a V- type bent shape.

Above that plane, there is one lone pair. It maintains the trigonal planner-like form after connecting the one terminal with the lone pair to the V-shaped bent form. The lone pair is located just opposite to bond pairs in the trigonal planner geometry. The one lone pair of the electron is just above the V-shape bent bond pair plane in trigonal planner geometry.

Because of the one lone pairs of electrons, it gives trigonal planner electron geometry. But the SO2 molecular geometry is a V-shape bent form in nature. It is the asymmetrical geometry of the SO2 molecule. That makes, SO2 molecule is polar.

How to find SO2 molecular geometry

Determine the number of lone pairs on the SO2 Lewis structure’s core Sulfur atom.
We need to figure out how many lone pairs there are on the central sulfur atom of the SO2 Lewis structure because the lone pairs on sulfur are primarily responsible for the SO2 molecule geometry distortion.

Use the formula below to find the lone pair on the SO2 molecule’s center Sulfur atom.
L.P(S) = V.E(S) – N.A(S-O)/2

Lone pair on the central sulfur atom = L.P(S)
The core central Sulfur atom’s valence electron = V.E(S)
Number of S-O bonds = N.A (S-O)
calculation for sulfur atom lone pair in SO2 molecule

In the case of SO2, the center atom, sulfur, has six outermost valence shell electrons and two oxygen atoms (four connections) connected to it.

As a result of this, L.P(S) = (6 – 4)/2=2

The lone pair on the center sulfur atom of the SO2 electron geometry structure is equal to one. It means, the central sulfur atom contains one lone pair of electrons.

Determine the number of SO2 molecular hybridizations.
How to find the hybridization of the SO2 molecule?. Now we need to figure out what SO2’s molecular hybridization number is.

The formula of SO2 molecular hybridization is as follows:
No. Hyb of SO2 = N.A(S-O) + L.P(S)
No. Hy of SO2= the number of hybridizations of SO2
Number of S-O bonds = N.A (S-O)
Lone pair on the central sulfur atom = L.P(S)
Calculation for hybridization number for SO2 molecule

Sulfur, then, is a central atom with two oxygen atoms linked to it and one lone pair in the SO2 molecule. Then the number of hybridization of SO2 (No. Hyb of SO2) can be calculated as follows

No. Hyb = 2+1 =3

The number of hybridization for SO2 molecule is three. one S orbital, and two p orbitals combine together to form the sp2 hybridization. This hybridization of SO2 molecule gives trigonal planner structure.

3. Use VSEPR theory to determine SO2 molecular geometry shape

When the VSEPR theory is utilized to calculate the shape of the SO2 molecule, the AXN approach is typically used.

The AXN notation is as follows:
The center sulfur atom in the SO2 molecule is denoted by the letter A.
The bound pairs (S-O) of electrons to the core atom are represented by X.
The lone pairs of electrons on the center sulfur atom are denoted by the letter N.
Notation for SO2 molecular geometry

We know sulfur is the center atom with two double bound (S-O) pairs of electrons and one lone pairs. because of the SO2 Lewis structure. SO2 has the general molecular geometry formula AX2N1.

If the molecule has an AX2N1 generic formula, the molecular geometry will be V- shape bent and the electron geometry will be trigonal planner, according to the VSEPR theory.

Name of Molecule	Sulfur dioxide
Chemical molecular formula	SO2
Molecular geometry of SO2	Bent V-shape
Electron geometry of SO2	Trigonal planner
Hybridization of SO2	Sp2
Bond angle (O-S-O)	119º degree
Total Valence electron for SO2	18
The formal charge of SO2 on sulfur	0

How to calculate the formal charge in SO2 Lewis Structure?

The formal charge on the sulfur central atom of the SO2 molecule often represents the actual charge on that sulfur central atom. The formal charge will be found on the central sulfur atom of the SO2 Lewis dot structure in the following calculation.

To calculate the formal charge on central sulfur atom of SO2 molecule by using the following formula:
The formal charge on Sulfur atom of SO2 molecule= (V. E(S)– L.E(S) – 1/2(B.E))
V.E (S) = Valence electron in sulfur atom of SO2 molecule
L.E(S) = Lone pairs of an electron in sulfur atom of SO2 molecule.
B.E = Bond pair electrons in S atom of SO2 molecule
calculation of formal charge on sulfur atom in SO2 molecule

We have 6 valence electrons, 2 lone pair electrons, and eight bonding electrons in the sulfur central atom (two double bonds attached to oxygen) of the SO2 molecule. Now put these value of the sulfur atom in the above formula

Formal charge on sulfur atom of SCl2 molecule = (6- 2-(8/2)) =0

The formal charge on central sulfur atom of SO2 Lewis structure is zero.

Lewis structure of some other related post in this blog. See more detail by clicking on it, H2O, BeCl2, SF4, NH3, XeF4, BF3, BrF3, BrF5, SO3,NH4+, SCl2, PCl3, H2S, NO2+,HBr, CS2, CH3F, and CH2Cl2 molecules.

The dipole moment of SO2

The dipole moment of the SO2 molecule can assist us in determining the polarity’s strength. The polarity of any molecule is proportional to its dipole moment. Because the form of SO2 is asymmetric. The dipole moment of SO2 does not cancel each other as a result of this.

The dipole moment of SO2 can be calculated as follows
D(S-O) = Q(S-O) * R(S-O)
D(S-O) = Dipole moment of S-O bond in SO2 molecule
Q(S-O) = Charge distribution in S and O atom of SO2 molecule
R(S-O)= Bond length of S-O bond in SO2 molecule
Dipole moment calculation of SO2 molecule

Net dipole moment of SO2 molecule is 1.62 D.

Why is SO2 a polar molecule?

Due to the existence of one lone pair on the central sulfur atom, the Sulfur dioxide (SO2) molecule has a twisted V- shape bent form. According to the VSEPR hypothesis, lone pairs and bond pairs repel each other, causing the S-O bonds to move the lower side of the trigonal planner molecular structure, resulting in a V-shaped SO2 molecule.

The dipole moment of S-O bonds does not cancel out as it does in asymmetric SO2 molecules. SO2 has a dipole moment of 1.62D across the entire molecule. The formation of a polar molecule is caused by the geometrical structure and the difference in electronegativity value of atoms in the SO2 molecule.

Because of the asymmetric shape of the SO2 molecule, the charge is dispersed non-uniformly among the sulfur and oxygen atoms, resulting in the formation of positive and negative poles across the SO2 molecule.

Physical Properties of SO2 molecule

Physical properties of SO2 listed as follows

Sulphur dioxide is a drab substance.
It has a very strong odour. It smells like smouldering sulphur.
It’s one of the easiest gases to work with when it comes to melting. This is due to the fact that it condenses at ambient temperature under a 2 atm pressure.

Chemical Properties of SO2 molecule

It’s a corrosive oxide.
It dissolves quickly in water.
Sulphuric acid is formed when sulphur dioxide combines with water.
It creates sodium sulphite when it interacts aggressively with sodium hydroxide solution.

Reaction with water:

SO2 reacted with water undergoes exothermic reaction and forms sulphurous acid.

SO2 + H2O ——–> H2SO3
SO2 reacted with water

Reaction with NaOH:

We get sodium hydrogen sulphite when we introduce more sulphur dioxide into alkali.

SO2 + 2NaOH → Na2SO3 + H2O
SO2 reacted with alkali(NaOH)

Reaction with Sodium sulfite:

In the cases that we pass more sulfur dioxide into this arrangement, we get sodium hydrogen sulfite.

SO2 + Na2SO3 → H2O + 2NaHSO3
SO2 reacted with sodium sulfite

Reaction with Cl2:

A sulphur dioxide atom’s sulphur particle is tetravalent. It can then increase its covalency to six by reacting with elements like as O2 and Cl2 to shape the corresponding addition compounds. For example, under the effect of charcoal as a catalyst, it combines with chlorine to produce sulphuryl chloride (SO2Cl2).

SO2 + Cl2 → SO2Cl2
reaction with Cl2

It produces sulphur trioxide in the presence of vanadium pentoxide (V2O5) as a catalyst.

2SO2 + O2 → SO3
Reaction with O2

Uses of SO2 molecule

The uses of SO2 molecule are listed below

As a food preservative in the food industry.
It works as a disinfectant and a bleaching agent to remove excess chlorine.
It functions as a refrigerant in cold storage plants.
In the laboratory, it is employed as a reagent and a solvent.
Inhaling sulphur dioxide causes major health problems such as early death and respiratory issues, thus precautions must be taken.

Conclusion

Due to the existence of one lone pairs on the central sulfur atom, sulfur dioxide(SO2) has a bent V-shape form. With a bond angle(O-S-O) of roughly 119 degrees, the sulfur atom is the center atom, surrounded by two oxygen atoms. Its electron geometry is trigonal planner. The molecular hybridization of the SO2 molecule is sp2.

Because of the difference in electronegativity between sulfur and oxygen atoms, the S-O bond is polar, and the entire SO2 molecule has a dipole moment of 1.62 D. This is due to the unsymmetrical structure of the SO2 molecule with one lone pair in a central sulfur atom. The SO2 molecule is polar due to its asymmetric geometrical shape and unequal electronegativity of its atoms.

If you have any queries and doubts about this SO2 polarity post, please leave your question in the comment section. We shall reply back on it as soon as possible.

FAQ on “Is SO2 polar or nonpolar?”

What causes acid rain when sulphur dioxide is released?

With water, oxygen, and other chemicals, SO2 and NOX combine to generate sulfuric and nitric acids. They then combine with water and other ingredients before dropping to the table.

What causes acid rain when sulphur dioxide is released?

Acid rain occurs when sulphur dioxide (SO2) and nitrogen oxides (NOX) are released into the atmosphere and carried by wind and air currents. With water, oxygen, and other chemicals, SO2 and NOX combine to generate sulfuric and nitric acids. They then combine with water and other ingredients before dropping to the table.

How acidic is sulphur dioxide?

In juices with high acidity, less sulphur dioxide is required; for example, 15 mg l1 of free sulphur dioxide at pH 3.0 has the same antibacterial activity as 150 mg l1 at pH 4.0. Sulfite, bisulfite, and molecular sulphur dioxide concentrations in aqueous solution as a function of pH.

Is sulphur dioxide an acid or a base?

Sulfur dioxide is an acid gas, which may be easily proved by filling a gas container with water and a few drops of universal indicator. Sulphurous acid (H2SO3) is formed, which is a slightly dibasic acid.

What causes sulphur dioxide to form?

Sulfur dioxide, or SO2, is a colourless gas or liquid with a pungent odour. It is made by smelting sulphur-bearing mineral ores and burning fossil fuels (coal and oil) (aluminum, copper, zinc, lead and iron). Sulphur dioxide dissolves rapidly in water, yielding sulfuric acid.

Is sulphur dioxide classified as a compound?

Sulfur dioxide (SO2) is an inorganic gas that is poisonous, viscous, and colourless. It is created in large amounts during the intermediate steps of the sulfuric acid production process. Sulfur dioxide has a harsh, unpleasant odour that resembles the smell of a freshly struck match.