Is H2Se Polar or Nonpolar? (And Why?)

H2Se is a POLAR molecule.

But why? 

And how can you say that H2Se is a polar molecule?

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

H2Se is a POLAR molecule because it has two lone pairs of electrons on the Selenium atom (Se) which causes the entire molecule to bend.
This bending of H2Se molecule results in asymmetric geometry, which makes the molecule polar.

Let me explain this in detail with the help of H2Se lewis structure and its 3D geometry.

Why is H2Se a Polar molecule? (Explained in 2 Steps)

To understand the polar nature of H2Se molecule, first of all you should know its lewis structure as well as its molecular geometry.

So let’s see this in the steps below.

Step #1: Draw the lewis structure

Here is a skeleton of H2Se lewis structure and it contains two H-Se bonds.

(Note: If you want to know the steps of drawing the H2Se lewis dot structure, then visit this article: H2Se lewis structure, Or you can also watch this short 2 minute video).

So from the above diagram we have come to know that the H2Se molecule has two H-Se bonds.

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

And we also have to check the molecular geometry of H2Se.

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 H2Se molecule. It has two H-Se bonds.

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

From the above image;

• Electronegativity of Hydrogen (H) = 2.2 ^[5]
• Electronegativity of Selenium (Se) = 2.55 ^[6]

Now let’s see the polarity of each bond.

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

But wait, we also have to look at the molecular geometry of H2Se to know whether it has a symmetric shape or not.

Have a look at this 3D structure of H2Se. The Selenium atom (Se) is at the center and it is surrounded by 2 Hydrogen atoms (H).

It also has two lone pairs on the Selenium atom (Se).

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

Because of this, there are positive and negative poles of charges on the overall molecule of H2Se.

Hence, the H2Se molecule is a polar molecule.

I hope you have understood the reason behind the polar nature of H2Se molecule.

See the polarity of other molecules to make your concepts clear:
Is AlCl3 Polar or Nonpolar?
Is COCl2 Polar or Nonpolar?
Is C3H8 (Propane) Polar or Nonpolar?
Is SiBr4 Polar or Nonpolar?
Is CHBr3 Polar or Nonpolar?