ClO3- Lewis Structure, Molecular Geometry, Hybridization, and Polarity


ClO3- or chlorine trioxide or chlorate is a monovalent inorganic anion that is soluble in water. Chlorine trioxide is non-combustible in nature but when it gets combined with combustible materials explosion is likely to occur.

The molecular weight of the compound is 83.45 g/mol.

ClO3- appears to be a wet substance mostly a solid which has moisture in it.

This compound can be made in a Redox reaction between chlorine and sodium hydroxide:

3Cl2​(g)​     +   6OH−(aq)   ​ ——>   5Cl−(aq)   ​+    ClO3−(aq)   ​+    3H2​O(l)​

If the question arose in your mind that what is a Redox reaction then let us tell you that it is a type of reaction in which the oxidation state of atoms is changed.

Here you can see the changes that occurred to the Chlorine atom.

The property of chlorates is that they are very powerful oxidizers and thus they should be kept away from materials that can be easily oxidized.

Thus, any kind of material which is easily combustible like sugar, charcoal, etc should not be brought near the ClO3- compound.

Another reaction that gives us the metal chlorates is when chlorine is added with hot metal hydroxides:

3Cl2   +   6KOH    ——>   5KCl   +   KClO3-   +   3H2O

Chlorates are highly toxic in nature but during reactions, they form chlorides which are not harmful in nature.
Now when we have read a little about what Chlorates are and how they are formed, let us move ahead and see their Lewis structure and geometry.


ClO3- Lewis Structure

Lewis’s structure is a very important concept if you want to understand more about the compound.

When we read about Lewis’s structure we get to know about the bond formation and position of different atoms in the plane.

Lewis’s structure is nothing but a method by which we can show pictorially how the bonds are formed and placed in a compound.

Let us move ahead step by step and see how the Lewis structure of ClO3- is made.

1. We have to first find the total number of valence electrons in the compound.

The valence electrons of Chlorine are 7. And as there is only one atom of Chlorine thus total valence electrons come to 7*1 = 7.

The valence electrons of Oxygen are 6. And as there are three atoms of Oxygen thus total valence electrons come to 6*3 = 18.

As we have told you in the introduction section that this compound is an anion. Thus, there is a negative charge on one of the oxygen atoms due to electron receiving.

That is equal to one valence electron.

Now to find the total valence electrons of the compound we will total the electrons of Oxygen, Chlorine, and one negative charge which is, =7+18+1 = 26.

2. Now we will find out about the lone pairs available.

The total number of valence pairs can be found by adding all the pi and sigma bonds the compound makes with lone electrons.

To find the valence pairs we will divide the total number of valence electrons by 2 because a pair can be made with the help of 2 electrons.

Here, the total pairs are 13 in number.

3. Find out the Central atom.

The central atom of this compound is Chlorine and there are three bonds made between Chlorine and Oxygen in the starting phase.

As you can see the picture shows the lone pair of electrons on the other atoms after the initial bonds are made.
Every oxygen atom has 3 lone pairs to complete its octet. So total lone pairs on oxygen alone are 9.

As we have seen that there are 3 bonds so after 9 lone pairs on oxygen we are left with only one lone pair which is assigned to Chlorine.

4. Balancing the charges.

To make the compound stable we will have to balance the charges.

For doing this we will change the bonding between the atoms.

Now you can see that the initial single bond is now changed to a double bond due to which the charge on Chlorine and Oxygen is reduced.

To make it more stable we have to convert the other single bonds into double bonds too.

Now there is only one charge in the whole compound which is acceptable.

There might come a question in your mind that why there are 12 electrons on Chlorine. This is because Chlorine can accept more than 8 electrons. This is because the 3d orbital in its electronic configuration is empty and can acquire more electrons.

So this is the most balanced Lewis structure of this compound.

This was a little complicated but we hope you grasped it nicely. Let us now move to the hybridization of this compound.

ClO3- lewis structure


Hybridization of ClO3-

The hybridization of the ClO3-  is sp3.

Why is it important to find the hybridization of a compound?

Hybridization is important because with its help we can find the most stable structure and geometry of a compound. The atomic orbitals are mixed to form new hybrid orbitals which are different in energy and shape.

This is what makes a compound unique and we get to know about its properties, structures, and geometry. We can find the hybridization of ClO3- by using the formula which is:

Hybridization = GA + (VE – V – C)/2

Here, GA is a group of atoms that are attached to the central atom, VE is valence electrons on the central atom, V is the Valency of the central atom and C is any charge on the molecule.

In ClO3-, the central atom is chlorine and its valency is 6 because there are three double bonds between chlorine and oxygen. The valence electrons on chlorine are 7. The atoms attached to chlorine are 3 and the charge is -1.


H = 3 + (7 – 6 – (-1))/2

H = 3 + (1 + 1)/2

H = 3 + 2/2

H = 3 + 1

H = 4

The value 4 denotes that the hybridization is sp3.

clo3- hybridization


Molecular Geometry of ClO3-

After learning about the hybridization and Lewis structure we can move to the molecular geometry of this compound.

But to properly understand its structure we have to know about the theory which helps us in deciphering the shape of any compound.

This theory is the VSEPR theory.

Lewis’s structure tells us about the shape of the compound but only in a 2D perspective.
If you want to know about how the compound is going to appear in 3D or a planar representation then we need VSEPR theory.

With the help of the VSEPR theory, we can also find the bond angles and bond length of compounds. Now let us find out the shape of ClO3-, the compound we are learning about.

To find the right shape we will need to take a look at the VSEPR model.

The general formula used here has A, X, and E representation.

Let us put our compound in this formula.

Here, A is Chlorine, X is Oxygen and E is the number of lone pairs on the central atom which in our case is Chlorine.

If we put the values correctly then we see the formula to come at AX3E. See the diagram above and find the shape corresponding to AX3E. It is Trigonal Pyramid.

We can also find the bond angle with the help of this deduction.

The bond angle between oxygen and chlorine atom is somewhere around 109 degrees. This angle is made due to the repulsion between lone pair of electrons and bonded pairs.

Now, as we have learned about the molecular shape of the compound let us move ahead and see what is the polarity of ClO3-.

ClO3- shape


The polarity of ClO3-

The polarity of any compound is nothing but charge separation which leads to a considerable dipole moment. A polar compound has a partial charge on the atoms.

Also, if a compound is polar their geometry is not symmetric.

Here, ClO3- does not have a symmetric geometry thus we can easily say that the compound is Polar in nature.


In a Nutshell

Now when we have reached the end of our discussion let us quickly rewind and see all the things that we have learned about this compound.

  • ClO3- is an inorganic anion in nature.
  • There is a negative charge on one of the neighboring oxygen atoms.
  • There are three double bonds in the structure.
  • The chlorine atom has more than 8 electrons in its outer shell.
  • The compound is polar in nature.
  • The hybridization of this compound is sp3.
  • The molecular geometry of this compound is a trigonal pyramid.

We hope that your concepts got clear for this particular compound.

In case you have any queries and doubts you can reach out to our team and we will get back to you with possible resolutions.

Thanks for reading!

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