NH3 (Ammonia) is a POLAR molecule.
And how can you say that NH3 is a polar molecule?
Want to know the reason?
Let’s dive into it!
NH3 (or Ammonia) is a POLAR molecule because the Nitrogen (N) 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 NH3 molecule polar.
Let me explain this in detail with the help of NH3 lewis structure and its 3D geometry.
Why is NH3 a Polar molecule? (Explained in 3 Steps)
NH3 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 NH3 lewis structure and it contains three N-H bonds.
(Note: If you want to know the steps of drawing the NH3 lewis dot structure, then visit this article: NH3 lewis structure).
So from the above diagram we have come to know that the NH3 molecule has three N-H bonds.
Now in the next step we have to check whether these N-H bonds are polar or nonpolar.
And we also have to check the molecular geometry of NH3.
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 2.0, then the bond is polar covalent bond.
- If the electronegativity difference (ΔEN) is greater than 2.0, then the bond is an ionic bond.
Now let’s come to the example of NH3 molecule. It has three N-H bonds.
You can see the electronegativity values of Nitrogen (N) and Hydrogen (H) atoms from the periodic table given below.
From the above image;
- Electronegativity of Nitrogen (N) = 3.04 eV
- Electronegativity of Hydrogen (H) = 2.2 eV
Now let’s see the polarity of each bond.
For N-H bond;
The electronegativity difference (ΔEN) = 3.04 – 2.2 = 0.84
This value lies between 0.4 to 2.0, which indicates that the bond between Nitrogen (N) and Hydrogen (H) is polar.
Hence, the N-H bond is a polar covalent bond.
You can see in the above image that because of higher electronegativity of Nitrogen atom, the partial positive charge (ẟ+) appears on the Hydrogen atoms (H) and partial negative charge (ẟ-) appears on the Nitrogen atom (N).
But wait, we also have to look at the molecular geometry of NH3 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 NH3. The Nitrogen atom (N) is at the center and it is surrounded by 3 Hydrogen atoms (H).
It also has one lone pair on the Nitrogen atom (N).
Due to the lone pair on the nitrogen atom (N), its molecular geometry becomes asymmetric.
Because of this, there are positive and negative poles of charges on the overall molecule of NH3.
Hence, the NH3 molecule is a polar molecule.
I hope you have understood the reason behind the nonpolar nature of NH3 (ammonia) molecule.
See the polarity of other molecules to make your concepts clear: