Is CH3NH2 Polar or Nonpolar? (And Why?)

CH3NH2 is a POLAR molecule.

But why? 

And how can you say that CH3NH2 is a polar molecule?

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

CH3NH2 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 CH3NH2 molecule polar.

Let me explain this in detail with the help of CH3NH2 lewis structure and its 3D geometry.

Why is CH3NH2 a Polar molecule? (Explained in 2 Steps)

CH3NH2 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 2 steps!

Step #1: Draw the lewis structure

Here is a skeleton of CH3NH2 lewis structure and it contains C-H bonds, C-N bond and N-H bonds.

(Note: If you want to know the steps of drawing the CH3NH2 lewis dot structure, then visit this article: CH3NH2 lewis structure, Or you can also watch this short 2 minute video).

So from the above diagram we have come to know that the CH3NH2 molecule has C-H bonds, C-N bond and N-H bonds.

Now in the next step we have to check whether these C-H bonds, C-N bond and N-H bonds are polar or nonpolar.

And we also have to check the molecular geometry of CH3NH2.

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]}

Now let’s come to the example of CH3NH2 molecule. It has C-H bonds, C-N bond and N-H bonds.

You can see the electronegativity values of Carbon (C), Hydrogen (H) and Nitrogen (N) atoms from the periodic table given below.

From the above image;

• Electronegativity of Carbon (C) = 2.55 ^[5]
• Electronegativity of Hydrogen (H) = 2.2 ^[6]
• Electronegativity of Nitrogen (N) = 3.04 ^[7]

Now let’s see the polarity of each bond.

For C-H bond;
The electronegativity difference (ΔEN) = 2.55 – 2.2 = 0.35 
This value is less than 0.4, which indicates that the bond between Carbon (C) and Hydrogen (H) is nonpolar.
Hence, each C-H bond is a nonpolar covalent bond.

For C-N bond;
The electronegativity difference (ΔEN) = 3.04 – 2.55 = 0.49
This value lies between 0.4 to 1.7, which indicates that the bond between Carbon (C) and Nitrogen (N) is polar.
Hence, the C-N bond is a polar covalent bond.

For N-H bond;
The electronegativity difference (ΔEN) = 3.04 – 2.2 = 0.84
This value lies between 0.4 to 1.7, which indicates that the bond between Nitrogen (N) and Hydrogen (H) is polar.
Hence, each 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 Carbon atom (C) as well as Hydrogen atoms (H) and partial negative charge (ẟ-) appears on the Nitrogen atom (N).

From this, you can easily get the idea that the CH3NH2 molecule is a polar molecule.

But let’s also see its 3D molecular geometry for better understanding.

Have a look at this 3D structure of CH3NH2. The more electronegative nitrogen atom (N) has a tendency to pull the shared electron pair towards itself, which results in partial positive charge on carbon atom (C) & hydrogen atom (H) and partial negative charge on nitrogen atom (N).

Because of this, there are positive and negative poles of charges on the overall molecule of CH3NH2.

Hence, the CH3NH2 molecule is a polar molecule.

I hope you have understood the reason behind the polar nature of CH3NH2 molecule.

See the polarity of other molecules to make your concepts clear:
Is SO3 2- Polar or Nonpolar?
Is AsF5 Polar or Nonpolar?
Is ClF Polar or Nonpolar?
Is CH3OCH3 Polar or Nonpolar?
Is BrCl3 Polar or Nonpolar?