We have all heard of the ozone layer depletion, haven’t we? Due to vast global warming and the rapid increase of temperature on earth, the ozone layer of the stratosphere has a hole in it.
This causes severe climate change and environmental damage. A pale blue gas with a molar mass of 47.99 g/ml, this molecular compound is often termed the activated oxygen.
It can be useful for killing bacterial growth and also releases a pungent smell.
Formed from the dioxide molecule, this molecule having three oxygen atoms is very crucial from the chemistry point of view. If you want to dive into his molecule, let us fasten our seat belts!
Because I am going to make you travel through all the essential concepts and explanations related to bonding within ozone.
To be very precise, Lewis Structure is the name given to the structural representation of a molecule. It is the diagrammatic layout for understanding the nitty-gritty of chemical bonding.
A very essential concept of molecular chemistry, the following steps dictate how you can successfully draw Lewis Structure:
The initial step towards forming this structure is to find out the total number of valence electrons.
‘+’ stands for positive charge i.e giving away(loss) of electrons.
‘-’ stands for the gain of electrons, or in other words, negative charge.
While calculating the valence electrons, we need to work with these two signs.
We now need to determine the central atom. How can we do so? We can easily find the solution to this with one simple trick!
First, point out the least electronegative atom. You can check this out by calculating the valence number. The one with the highest valence usually has the least electronegativity.
This atom will consist of higher sites of bonding compared to the others.
In this step, the task is to visualize the position of single bonds present in the molecule as a whole to the central atom.
This is carried out by sketching the skeleton diagram of the respective molecules as per requirements
Do you know that when atoms contain less than eight electrons in their outermost electron shell, they are still in their reactive state?
Hence, they react accordingly and tend to form more stable molecular compounds. So, the octet rule is based on the fact that every atom should have eight electrons in its valence shell.
The fourth step of Lewis Structure formation is based on achieving this. Starting with the electropositive ones, slowly fulfill the octet of the atoms.
Once, octet fulfillment has been done, we now need to find out if bond formation is left. Accordingly, multiple bond formation can be done.
We are now done with all kinds of bond formation, The last step is focused on the formal charge concept.
The bond formation (single and multiple ones) leads us to the final step of the process, i.e. the sixth step. Here, we will focus on calculating the formal charge.
We need to check whether all the atoms inside the given molecule are maintained at their least formal charge.
Below is the formula for formal charge:
Lewis Structure of O3
Here, we will be dealing with ozone, the molecular formula is O3.
The below discussion, therefore, will be based on finding out the Lewis Structure of O3.
Ozone consists of three oxygen atoms. Oxygen belongs to group VI of the periodic table with an atomic no of 8.
It thus has 6 valence electrons.
Thus, the total number of valence electrons in ozone= 3*6
Just like triiodide ion where all the atoms are iodine, here, all the atoms are oxygen. So, we will just consider one of the three to be the central atom and place the other two on lateral sides.
Now, we will draw the skeletal structure of ozone based on step no. 3. While drawing, let us now place the valence shell electrons( total count=18) for octet fulfillment.
As discussed above, we can place six electrons surrounding each oxygen as per the periodic table knowledge.
Have a look at the above diagram now.
You can see that the side oxygen atoms have both achieved octet. They both have eight electrons surrounding them. But, the central atom only has six electrons around itself.
So, to fulfill the octet rule, what we need to do is:
We have to shift two electrons from either one lateral oxygen atom and place it beside the central oxygen atom.
The octet formation is now successful.
We now have one double bond and one single bond concerning the central O atom.
Since we could have drawn, either way, we now have resonance structures. After checking the formal charge, the final Lewis Structure or electron dot structure of O3 has been done.
Hybridization of O3
What do we mean by hybridization? Why is this such a common topic in chemical bonding and why do we need to study this?
Well, hybridization is one of the vast and major topics in molecular chemistry.
It refers to the process of intermixing orbitals to form hybrid orbitals. How and why several atoms tend to combine with one another forms the basis of hybridization.
Hence, the study is important to know more in detail about a molecule and its properties.
To learn about ozone, therefore, we need to have some knowledge about its hybridization.
Now, how can we find out here?
How many electrons does the central oxygen atom have? 8.
2s orbital has two electrons and the rest six are present in 2px and 2py.
Total no of orbitals= 1s and 2p
Hence, the hybridization of the O3 molecule is sp2.
Molecular Geometry of O3
To find out the molecular geometry of ozone we need to check the VSEPR theory model.
How to proceed with this?
At the very beginning, you have to check the terminal atoms.
Terminal atom no.= 2
Now, find out the no of lone electrons or lone pairs
Lone electrons=2 in the central atom
After this, we have to match this with the VSEPR model graph
The ozone molecule is found to be bent trigonal planar shape due to the presence of resonance. Repulsion causes the bond angle to come to about 116 degrees.
The polarity concept is based on the distribution of positive and negative charges inside a molecule surrounding the constituent atoms.
The dipole moment is used to measure or calculate the polarity. This only has a net value when there is a charge difference.
In the case of ozone, the usual dipole moment value varies and there is the presence of partial + and + charges inside the molecule.
The ozone atom at the center will carry the partial+ + charge.
Dipole moments then are responsible for moving the ozone molecule in a downward direction The lone electron pair results in a net dipole in O3 and hence the ozone molecule is considered to be polar in nature.
O3 Molecular Orbital Diagram (MO)
The molecular orbital theory is one of the major revolutionary concepts of chemical bonding.
It uses quantum mechanics to give us a detailed almost explanatory diagram of the bonding nature inside a molecule.
Here is a diagrammatic representation of the MO diagram of ozone.
Ozone is a trigonal planar molecule. Hence, as we take one p orbital from each atom of oxygen(O3), we focus on the 4 electron H3- anion.
According to hybrid orbital approximation, we will consider the 2s, 2py, and 2pz orbitals. Then we will perform semi-empirical Molecular Orbital calculations and involve the concept of group orbitals.
Chemical bonding is indeed one of the vast and yet very important chapters for the entire life. If you are here to learn small details about any molecule, you have come to the right place.
Now that you have gone through the major concepts of the ozone molecule in detail, I hope you have got a basic understanding.
We have discussed Lewis structure and Hybridization. We have mentioned the shape and the polarity of the molecule and also the MO Diagram. So, did you have a good time?
I think so. Always keep learning.