NH2- ion is a POLAR ion.
And how can you say that NH2- is a polar ion?
Want to know the reason?
Let’s dive into it!
NH2- ion is a POLAR ion because the N-H bonds present in the ion are polar and it has asymmetric geometry which causes the partial positive (ẟ+) and partial negative (ẟ-) charge to appear on the ion. These ẟ+ and ẟ- charges are responsible to make the entire NH2- ion polar.
Let me explain this in detail with the help of NH2- lewis structure and its 3D geometry.
Why is NH2- ion a Polar ion? (Explained in 3 Steps)
NH2- ion is a polar ion 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 NH2- lewis structure and it contains two N-H bonds.
(Note: If you want to know the steps of drawing the NH2- lewis dot structure, then visit this article: NH2- lewis structure, Or you can also watch this short 2 minute video).
So from the above diagram we have come to know that the NH2- ion has two 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 NH2- ion.
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.    
Now let’s come to the example of NH2- ion. It has two 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;
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 1.7, 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 NH2- ion to know whether it has a symmetric shape or not.
Step #3: Check whether the ion is symmetric or not
Have a look at this 3D structure of NH2- ion. The Nitrogen atom (N) is at the center and it is surrounded by 2 Hydrogen atoms (H).
It also has two lone pairs on the Nitrogen atom (N).
Due to the lone pairs on the nitrogen atom (N), its molecular geometry becomes asymmetric.
Because of this, there are positive and negative poles of charges on the overall NH2- ion.
Hence, the NH2- ion is a polar ion.
I hope you have understood the reason behind the polar nature of NH2- ion.
Jay is an educator and has helped more than 100,000 students in their studies by providing simple and easy explanations on different science-related topics. With a desire to make learning accessible for everyone, he founded Knords Learning, an online learning platform that provides students with easily understandable explanations.
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