Is Sulfur dioxide (SO2) ionic or covalent? Types of bond in SO2
Is SO2 ionic or covalent? SO2 is a covalent molecule. Because the bond is formed between one atom of sulfur (S) and two atoms of oxygen (O) by the sharing of electrons. The difference in electronegativity between sulfur (S) and oxygen (O) atoms on the Pauling scale is not big enough to make an ionic bond in the SO2 compound.
Let’s discuss in detail, Is Sulfur dioxide (SO2) ionic or covalent? Bond types, etc.
Sulfur dioxide is made up of one sulfur and two oxygen atoms that have a pungent odor similar to a just-struck match and appear as colorless gas having the chemical formula SO2. It is soluble in water very easily and becomes liquid when under pressure. It is a toxic gas and can cause severe health hazards when exposed to it for a long time.
A covalent compound is a chemical compound that is made when two nonmetals or two p-block elements together share their valence electrons with each other to complete the octet and attains stability.
The sharing of valence electrons between two atoms makes a bond which is called a covalent bond. “Valence electrons are the outermost shell electron of an atom”.
Sulfur dioxide (SO2) is a covalent compound. Because the sulfur (S) and oxygen (O) atoms are nonmetals in nature, they don’t have any tendency to either accept or donate the electrons but both sulfur and oxygen atoms have a tendency to share their valence electron with each other and hence, complete the octet and makes a stable SO2 covalent compound.
As we see in the above figure, the three atoms(two oxygen and one sulfur) share a total of eight electrons with each other through the help of two double bonds. Hence, the bond formed in the SO2 compound is covalent in nature as shared bonding electrons occur between the sulfur and oxygen atom.
Examples of some compounds that form covalent bonds – are H2O, H2S, NH3, NO2, AlCl3, etc.
The covalent bond is formed in SO2 because of sharing of electrons occur between sulfur and oxygen atom.
Let’s see how covalent bond formation takes place in SO2.
First of all, there are two types of atoms present in the sulfur dioxide molecule – sulfur and an oxygen atom.
⇒ The sulfur atom is a nonmetal that belongs to Group 16 or 6A in the periodic table and has six valence electrons in the outermost shell.
⇒ The oxygen atom is also a nonmetal that also belongs to Group 16 or 6A in the periodic table and has a 6 valence electron in its outermost shell.
Every atom wants to complete its octet i.e. having 8 electrons in the outermost shell and attaining stability. Atoms can complete their octet by bonding with other elements or atoms with the help of either sharing of electrons or the complete transfer of electrons.
In the case of an SO2 molecule, when sulfur and oxygen atoms are placed together, they will share the electrons with each other to complete their octet and hence, makes a covalent bond.
Both sulfur and oxygen atom needs two more electrons to complete their octet, hence, both of these(one sulfur and two oxygen atoms) shares a total of 8 valence electrons with each other.
Sulfur shares a total of four valence electrons with the two oxygen atoms. Each oxygen atom shares two valence electrons with sulfur.
The three atoms(one sulfur and two oxygen atoms) will share a total of eight valence electrons, the equivalent of two double bonds.
Therefore, the bond formed between sulfur and oxygen atom is covalent in nature.
Note: The lone pair electrons can never take parts in chemical bonding or they never share electrons with any of the atoms. The shared pair of electrons is also called bonded pair of electrons.
Why is SO2 not a ionic compound?
The SO2 molecule is not an ionic compound because the difference in electronegativity value between sulfur and an oxygen atom is not big enough to make an ionic bond between them according to the Pauling scale.
According to the Pauling scale of electronegativity-
The covalent bond is formed between the two atoms when their electronegativity difference occurs less than 1.7.
The ionic bond is formed between the two atoms when their electronegativity difference occurs more than 1.7.
Now check the electronegativity difference in SO2 molecule-
⇒ The electronegativity value for sulfur atom = 2.58
⇒ The electronegativity value for oxygen atom = 3.4
∴ The difference in the electronegativity between sulfur and oxygen atoms = 0.82
So, the difference in electronegativity value between sulfur and oxygen atom is less than 1.7, hence, it is low enough to make a covalent bond between them as per the Pauling scale of electronegativity.
Also, the main difference between ionic and covalent is that an ionic bond is formed when either donating or accepting the electrons occurs between two atoms, and a covalent bond is formed when only sharing of electrons occurs between two atoms.
The sulfur and oxygen atoms in the SO2 molecule can never transfer their electrons because their octet can be completed only when they share the electrons with each other, hence, the bond formed in the SO2 molecule is covalent in nature rather than ionic.
Examples of some ionic compounds – MgO, Na2O, MgCl2, NaCl, etc.
So, Is SO2 a pure covalent bond? No, it is not. First of all, understand the actual means of a pure covalent bond.
We know, SO2 is a covalent compound but whether it is pure or not that depends on the sharing of electrons that occur between the atoms(sulfur and oxygen).
A pure covalent bond is formed when the electronegativity values of the two or more atoms in a molecule are the same. If the electronegativity value is the same for two atoms, then the sharing of electrons between them is also equal, hence, the bond forms between them are pure covalent in nature.
In short, a pure covalent bond is formed between the atoms when they share an equal number of electrons.
But SO2 or sulfur dioxide molecule is not a pure covalent compound because the difference in electronegativity value in sulfur(2.58) and oxygen(3.4) caused unequal sharing of electrons between them.
The electrons are more shared towards the oxygen atom as it is more electronegative than sulfur, hence, unequal sharing of electrons occurs in the SO2 compound, which makes it a not pure covalent compound.
Is SO2 polar covalent or nonpolar covalent compound?
A polar covalent compound is formed when the unequal sharing of electrons occurs between two atoms because of their difference in electronegativity value.
When the difference in electronegativity value between two atoms lies between 0.4 to 1.7, then the bond formed between two atoms is polar in nature according to the Pauling scale of electronegativity.
A nonpolar covalent compound is formed when the equal sharing of electrons occurs between two atoms because of the very little difference in their electronegativity value.
When the difference in electronegativity value between two atoms is less than 0.4, then the bond formed between two atoms is nonpolar in nature according to the Pauling scale of electronegativity.
So, Is SO2 a polar covalent or nonpolar covalent compound? SO2 is a polar covalent compound because the electronegativity difference between sulfur and an oxygen atom is 0.82 which is in the range of the Pauling scale of the polar compound from 0.4 to 1.7.
Also, the unequal sharing of electrons occurs in SO2 molecules because oxygen(3.4) is higher electronegative than a sulfur atom(2.58), therefore, it will pull more electrons towards itself, hence, the oxygen atom induced a negative charge on it and sulfur atoms get a slightly positive charge.
The separation of charges generates the dipole moment directed from positive to negative, hence, due to all these a bond is formed between sulfur and oxygen, which is called a polar bond.
It has a pungent odor similar to a just-struck match.
It has a boiling point of −10 °C and a melting point of −72 °C.
It has a dipole moment of 1.62 D.
It is a bent molecule and has a diagonal coordination geometry.
Sulfur dioxide is the third most significant gas in the atmosphere of Venus.
It is a strong oxidizing agent and also acts as a reducing agent.
It is not combustible.
Uses of sulfur dioxide
It is commonly used as a food preservative in food industries.
It is used as an antioxidant to prevent rotting in fruits.
It is used to preserve the colors of soft drinks.
It is used as a bleaching agent and as well as a disinfectant.
It is used as a reagent and a solvent in the laboratory.
FAQ
How many covalent bonds are present in an SO2 molecule?
A covalent bond is formed when sharing of electrons is done between the atoms to achieve the noble gas configuration.
“SO2 has two double covalent bonds, 1 with each oxygen atom.
Why is SO2 polar covalent compound?
SO2 is a polar covalent compound. Because the electronegativity difference between sulfur and an oxygen atom is 0.82 which is in the range of the Pauling scale of the polar compound from 0.4 to 1.7.
Also, the unequal sharing of electrons occurs in SO2 molecules because oxygen(3.4) is higher electronegative than a sulfur atom(2.58), hence, it will pull more electrons towards itself, hence, the oxygen atom induced a negative charge on it and sulfur atoms get a slightly positive charge.
The separation of charges generates the dipole moment directed from positive to negative, hence, due to all these a bond is formed between sulfur and oxygen, which is called a polar bond.
Summary
Is Sulfur dioxide (SO2) ionic or covalent? SO2 is a covalent compound. Because the difference in electronegativity between sulfur (S) and oxygen (O) is low enough to result in sharing of electrons which leads to the formation of a covalent bond in SO2.
The covalent bond formed in the SO2 molecule is polar in nature.
SO2 is not a pure covalent compound because of the unequal sharing of electrons between atoms.
The difference in electronegativity between Oxygen (O) and Sulfur(S) is 3.4–2.58=0.82 which is lower than 1.7, hence, according to the Pauling scale, the bond formed between oxygen (O) and a sulfur (S) atom is covalent, that makes, SO2 compound, covalent in nature.
Vishal Goyal is the founder of Topblogtenz, a comprehensive resource for students seeking guidance and support in their chemistry studies. He holds a degree in B.Tech (Chemical Engineering) and has four years of experience as a chemistry tutor. The team at Topblogtenz includes experts like experienced researchers, professors, and educators, with the goal of making complex subjects like chemistry accessible and understandable for all. A passion for sharing knowledge and a love for chemistry and science drives the team behind the website. Let's connect through LinkedIn: https://www.linkedin.com/in/vishal-goyal-2926a122b/
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