Is ClO2- Polar or Nonpolar? (And Why?)

ClO2- (Chlorite ion) is a POLAR ion.

But why? 

And how can you say that ClO2- ion is a polar ion?

Want to know the reason?
Let’s dive into it!

ClO2- ion is a POLAR ion because it has two lone pairs of electrons on the Chlorine atom (Cl) which causes the entire ion to bend.
This bending of ClO2- ion results in asymmetric geometry, which makes the ion polar.

Let me explain this in detail with the help of ClO2- lewis structure and its 3D geometry.

Why is ClO2- ion a Polar ion ? (Explained in 2 Steps)

To understand the polar nature of ClO2- ion, first of all you should know its lewis structure as well as its molecular geometry.

So let’s see this in the steps below.

Step #1: Draw the lewis structure

Here is a skeleton of ClO2- lewis structure and it contains two Chlorine-Oxygen bonds.

(Note: If you want to know the steps of drawing the ClO2- lewis dot structure, then visit this article: ClO2- lewis structure, Or you can also watch this short 2 minute video).

So from the above diagram we have come to know that the ClO2- ion has two Chlorine-Oxygen bonds.

Now in the next step we have to check whether these two Chlorine-Oxygen bonds are polar or nonpolar.

And we also have to check the molecular geometry of ClO2- ion.

Step #2: Check the bond polarity and molecular geometry

The chemical bonds can be either nonpolar, polar or ionic depending on the difference of the electronegativity values (ΔEN) between the two atoms.

Have a look at the above image.

• If the electronegativity difference (ΔEN) is less than 0.4, then the bond is nonpolar covalent bond.
• If the electronegativity difference (ΔEN) is between 0.4 to 1.7, then the bond is polar covalent bond. 
• If the electronegativity difference (ΔEN) is greater than 1.7, then the bond is an ionic bond. ^{[1] [2] [3] [4] [5]}

Now let’s come to the example of ClO2- ion. It has two Chlorine-Oxygen bonds.

You can see the electronegativity values of Chlorine (Cl) and Oxygen (O) atoms from the periodic table given below.

From the above image;

• Electronegativity of Chlorine (Cl) = 3.16 ^[6]
• Electronegativity of Oxygen (O) = 3.44 ^[7]

Now let’s see the polarity of each bond.

For Chlorine-Oxygen bond;
The electronegativity difference (ΔEN) = 3.44 – 3.16 = 0.28
This value is less than 0.4, which indicates that the bond between Chlorine (Cl) and Oxygen (O) is nonpolar.
Hence, each Chlorine-Oxygen bond is a nonpolar covalent bond.

But wait, we also have to look at the molecular geometry of ClO2- ion to know whether it has a symmetric shape or not.

Have a look at this 3D structure of ClO2- ion. The Chlorine atom (Cl) is at the center and it is surrounded by 2 Oxygen atoms (O).

It also has two lone pairs on the Chlorine atom (Cl).

Due to the lone pair on the chlorine atom (Cl), its molecular geometry becomes asymmetric.

Because of this, there are positive and negative poles of charges on the overall ClO2- ion.

Hence, the ClO2- ion is a polar ion.

I hope you have understood the reason behind the polar nature of ClO2- ion.

See the polarity of other molecules to make your concepts clear:
Is XeCl4 Polar or Nonpolar?
Is NOBr Polar or Nonpolar?
Is GeH4 Polar or Nonpolar?
Is Isopropanol (C3H8O) Polar or Nonpolar?
Is Butane (C4H10) Polar or Nonpolar?