Silicon dioxide, also known as silica, is a compound with the chemical formula SiO2. It is made up of one silicon atom and two oxygen atoms. The majority of it is found in sand.
In this article, we’ll look at the Lewis structure of silicon dioxide (SiO2), molecular geometry, whether it’s polar or non-polar, hybridization, and bond angle, among other things.
Silicon Dioxide (SiO2) Lewis Structure
The Lewis structure of SiO2 is identical to the Lewis structure of CO2. The only difference is that instead of carbon, silicon is used.
One silicon atom is at the middle, with two oxygen atoms bound to it in a double bond. There are no lone pairs on the central atom of the SiO2 Lewis dot structure,
Let’s take a look at how to do this step by step.
Step 1: Count the total number of valence electrons in SiO2.
The first step is to determine how many valence electrons SiO2 has. Since silicon is in the 14th group of the periodic table and oxygen is in the 16th group, silicon has a 4 valence electron and oxygen has 6.
Oxygen’s electronic configuration = 1s2 2s2 2p4
Silicon’s electronic configuration = 1s2 2s2 2p6 3s2 3p2
Hence, No. of valence electrons in oxygen = 6
No. of valence electrons in Silicon = 4
The total number of valence electrons available in the Lewis structure of SiO2 is 4 + 2*6 = 16 electrons.
Step 2: Find the atom with the least electronegativity and position it in the middle.
We’ll look for the least electronegative atom between silicon and oxygen and place it in the center of the SiO2 Lewis structure.
We learned that silicon is less electronegative than oxygen as electronegativity increases from left to right in the periodic table.
So, place silicon in the middle, and oxygen is equally spaced around it.
Step 3: Using a single bond, connect all oxygen atoms to the silicon atom.
We used two single bonds in the structure since one single bond contains two electrons. It means that out of a total of 16 valence electrons, we used 4 of them.
Step 4: Starting with the outer atom, position the remaining valence electrons.
Now, we have an extra 12 valence electrons.
Position the remaining valence electron around the outer atom (oxygen) first. We need 12 more valence electrons to complete the octet, and oxygen needs 8 electrons.
However, oxygen already shares two electrons via a single bond. As a result, add six more electrons to each oxygen atom.
From the total of 12 remaining valence electrons, we have put 6 electrons around each oxygen atom.
However, this structure is not yet stable since silicon only has four electrons surrounding it and requires four more to complete its octet.
Let’s finish it up in the next step.
Step 5: Complete the central atom octet and, if possible, form a covalent bond.
This is the last step in completing the Lewis diagram for SiO2. As we all know, silicon needs 8 electrons to complete its octet, but it only has 4 electrons right now.
By turning an oxygen atom’s electrons into a covalent bond, we would be able to achieve the octet of silicon.
We convert two lone pairs of electrons from each oxygen atom to a covalent bond, as seen in the SiO2 Lewis dot structure. As a result, the valence shells of both silicon and oxygen have eight electrons.
SiO2 Molecular Geometry and Hybridization
The VSEPR theory can be used to determine the molecular geometry of SiO2. Let’s take a look at how to do it.
To determine the molecular geometry of SiO2, follow these steps.
1. Find out SiO2 hybridization.
What is the concept of SiO2 hybridization? We must first determine its hybridization number. We have a formula for this.
Hybridization Number = Number of atoms attached to the central atom + lone pairs on that central atom
Silicon is the central atom. It has no lone pair on it but has two atoms attached to it.
Hybridization number = 2 + 0 = 2
This means hybridization of SiO2 is Sp.
Determine the number of bond pairs and lone pairs in the Lewis structure of SiO2.
There are no lone pairs of electrons on the central atom of the Silicon dioxide Lewis structure. There are also two bond pairs, one between oxygen and silicon and the other between silicon and oxygen.
As a result, there are no lone pairs and two bond pairs.
According to the VSEPR theory, if a molecule has Sp hybridization and two bond pairs, but no lone pair on the central atom, the molecule’s molecular and electron geometry is linear.
Let me give you a brief description of the VSEPR Theory
Sidgwick and Powell’s VSEPR theory provides a basic method for predicting the form of a covalent molecule. The repulsive interactions between the valance electrons of the atoms are the basis for this theory.
The bond pairs find a position in space to minimize repulsive interactions and increase the distance between them due to electron repulsion. Lone pairs are non-bonded valence electrons and have more repulsions than bond pairs.
Let’s look at the VSEPR chart and see how it works.
From the above chart, SiO2 molecular geometry has the generic formula AX2.
Since there is no lone pair on the central atom of the SiO2 Lewis dot diagram, the bond angle is 180 degrees. This means there is no impact on the bond angle since there is no repulsion between the lone and bond pair.
According to VSEPR theory, “The geometry around an atom with just two bonds and no unshared electrons is a straight line,”
Is SiO2 Polar or Non-polar?
Since the net dipole moment is zero, SiO2 is clearly non-polar. The majority of molecules with Sp hybridization and linear molecular geometry are non-polar because the dipole moment formed along with the bond is easily canceled.
The Si-O bond on both sides of SiO2 is symmetrically arranged, canceling out the dipole since the same magnitude is present on both sides.
The factors that affect polarity are described below:
The greater the difference in electronegativity of atoms, the greater the polarity between those atoms. Silicon has an electronegativity of about 1.95, while oxygen has an electronegativity of 3.45.
Electronegativity difference = 3.45 – 1.95 = 1.5
As a result of the difference in electronegativities between silicon and oxygen, the Si-O bond is polar. However, the molecule as a whole is nonpolar due to its symmetric geometry.
In SiO2, the net dipole moment is zero because two dipole moments are formed in opposite directions from silicon to oxygen.
As there is an evenly distributed charge all over and the arrangement is also symmetrical, dipoles cancel each other out.
Dipole moment = charge on the atoms * the distance between them.
We know that the molecular form of SiO2 is linear, which is highly symmetrical. And that the Lewis structure of Silicon dioxide does not have any lone pairs of electrons.
So there is no shape distortion, making it easy to cancel out the dipole moment produced by the Si-O bond.
As a result of all of these factors, SiO2 is a non-polar molecule.
Silicon Dioxide Uses
Silicon dioxide has a variety of applications. A few of them are listed below.
- Silicon dioxide is used as a sedative.
- It’s used in the pharmaceutical industry.
- It finds application in the food industry as a flavor enhancer.
- It is used to make powdered ingredients less sticky.
- It’s used as an anti-caking agent.
- It is used in the manufacture of concrete and cement.
SiO2 has a net dipole moment of zero. It has a linear electron and molecular geometry with a bond angle of 180 degrees and a hybridization of Sp. The Silicon dioxide Lewis structure has a total of 16 valence electrons. In the Lewis dot structure of SiO2, the formal charge is zero.
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