Is H2O (Water) Polar or Nonpolar? (And Why?)

H2O (Water) is a POLAR molecule.

But why? 

And how can you say that H2O is a polar molecule?

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

H2O (or Water) is a POLAR molecule because the Oxygen (O) present in the molecule is more electronegative, which causes the partial positive (ẟ+) and partial negative (ẟ-) charge to appear on the molecule. These ẟ+ and ẟ- charges are responsible to make the entire H2O molecule polar.

Let me explain this in detail with the help of H2O lewis structure and its 3D geometry.

Why is H2O a Polar molecule? (Explained in 3 Steps)

H2O is a polar molecule because it has poles of partial positive charge (ẟ+) and partial negative charge (ẟ-) on it.

Let me explain this to you in 3 steps!

Step #1: Draw the lewis structure

Here is a skeleton of H2O lewis structure and it contains two O-H bonds.

(Note: If you want to know the steps of drawing the H2O lewis dot structure, then visit this article: H2O lewis structure, Or you can also watch this short 2 minute video).

So from the above diagram we have come to know that the H2O molecule has two O-H bonds.

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

And we also have to check the molecular geometry of H2O.

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 H2O molecule. It has two O-H bonds.

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

From the above image;

• Electronegativity of Oxygen (O) = 3.44 ^[6]
• Electronegativity of Hydrogen (H) = 2.2 ^[7]

Now let’s see the polarity of each bond.

For O-H bond;
The electronegativity difference (ΔEN) = 3.44 – 2.2 = 1.24
This value lies between 0.4 to 1.7, which indicates that the bond between Oxygen (O) and Hydrogen (H) is polar.
Hence, the O-H bond is a polar covalent bond.

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

But wait, we also have to look at the molecular geometry of H2O to know whether it has a symmetric shape or not.

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

Have a look at this 3D structure of H2O. The Oxygen atom (O) is at the center and it is surrounded by 2 Hydrogen atoms (H).

It also has two lone pairs on the Oxygen atom (O).

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

Because of this, there are positive and negative poles of charges on the overall molecule of H2O.

Hence, the H2O molecule is a polar molecule.

I hope you have understood the reason behind the polar nature of H2O (water) molecule.

See the polarity of other molecules to make your concepts clear:
Is SO2 Polar or Nonpolar?
Is CS2 Polar or Nonpolar?
Is Hydrogen Chloride (HCl) Polar or Nonpolar?
Is BF3 Polar or Nonpolar?
Is H2S Polar or Nonpolar?