Is CO3 2- Polar or Nonpolar? (And Why?)

CO3 2- ion is a NONPOLAR ion.

But why? 

And how can you say that CO3 2- is a nonpolar ion?

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

CO3 2- is a NONPOLAR ion because all three bonds (C=O bond and C-O bonds) are polar but CO3 2- has symmetrical geometry which cancels out the bond polarity.

Let me explain this in detail with the help of CO3 2- lewis structure and its 3D geometry.

Why is CO3 2- a Nonpolar ion? (Explained in 3 Steps)

CO3 2- ion is a nonpolar ion because it does not have any pole of positive charge and negative charge on it.

Let me explain this to you in 3 steps!

Step #1: Draw the lewis structure

Here is a skeleton of CO3 2- lewis structure and it contains two C-O bonds and one C=O bond.

(Note: If you want to know the steps of drawing the CO3 2- lewis dot structure, then visit this article: CO3 2- lewis structure, Or you can also watch this short 2 minute video).

So from the above diagram we have come to know that the CO3 2- ion has two C-O bonds and one C=O bond.

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

Step #2: Check whether individual bonds are polar or nonpolar

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 CO3 2- ion. It has two C-O bonds and one C=O bond.

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

From the above image;

• Electronegativity of Carbon (C) = 2.55 ^[6]
• Electronegativity of Oxygen (O) = 3.44 ^[7]

Now let’s see the polarity of each bond.

For Carbon-Oxygen bond;
The electronegativity difference (ΔEN) = 3.44 – 2.55 = 0.89
This value lies between 0.4 to 1.7, which indicates that the bond between Carbon (C) and Oxygen (O) is polar.
Hence, each Carbon-Oxygen bond is a polar covalent bond.

You can see in the above image that because of electronegativity difference, the partial positive charge (ẟ+) appears on the Carbon atom (C) and partial negative charge (ẟ-) appears on the Oxygen atoms (O).

But wait, this alone won’t tell you whether the entire CO3 2- ion is polar or nonpolar.

So let’s proceed to the next step to check the symmetry of the CO3 2- ion.

Step #3: Check whether the ion is symmetric or not

Have a look at this 3D structure of CO3 2- ion. You can see that the structure of CO3 2- ion is symmetrical. 

The carbon atom is at the center and it is surrounded by 3 oxygen atoms which are equidistant as well as at equal angles.

As the CO3 2- ion has a symmetrical geometry, their bond polarity gets canceled with each other.

Because of this, there are no positive and negative poles of charges on the overall CO3 2- ion.

Hence, the CO3 2- ion is a nonpolar ion.

I hope you have understood the reason behind the nonpolar nature of CO3 2- ion.

See the polarity of other molecules to make your concepts clear:
Is COF2 Polar or Nonpolar?
Is SeO3 Polar or Nonpolar?
Is Acetic acid (CH3COOH) Polar or Nonpolar?
Is H3O+ Polar or Nonpolar?
Is BBr3 Polar or Nonpolar?