HI is a covalent (polar covalent) compound because when one nonmetal combines with another nonmetal, it usually forms a covalent compound. Here, H (hydrogen) is a nonmetal and I (iodine) is also a nonmetal. So when they combine, it forms a covalent compound.
Well, now you have got to know that HI is a covalent compound, but let me explain the in-depth reason why HI is a covalent compound.
If you are a visual learner like me, then here is a short one minute video for you.
Why is HI a Covalent compound?
As mentioned above, you can simply remember that when the nonmetal combines with another nonmetal, the bond between them is a covalent bond.
Here in HI, the H atom is a nonmetal and the I atom is also a nonmetal.
Hence the bond between them is a covalent bond.
How does the covalent bond form between H and I?
In HI, there are two atoms;
H and I.
About Hydrogen (H):
Hydrogen atom have 1 electron.
It has only 1 orbit and there is only 1 electron in this orbit.
Now in order to achieve a stable duplet, the Hydrogen atom needs 1 more electron.
Hence during the chemical reaction, the Hydrogen atom will gain 1 electron from the combining atom to form a stable duplet.
About Iodine (I):
Iodine atom have 53 electrons.
The electrons arrangement in Iodine (I) is 2, 8, 18, 18, 7.
So the outermost orbit of an Iodine atom has 7 electrons.
Now in order to achieve a stable octet, the Iodine atom needs 1 more electron.
Hence during the chemical reaction, the Iodine atom will gain 1 electron from the combining atom to form a stable octet.
What happens when H and I combine?
When H and I combine with each other, the Hydrogen atom and Iodine atom mutually share their 1-1 electrons with each other.
Because of this the hydrogen atom will have 2 electrons in its outermost orbit and similarly the iodine atom will also have 8 electrons in its outermost orbit.
As a result, the hydrogen atom will have a stable duplet and the iodine atom will have a stable octet.
And finally, as the bond formed between the hydrogen and iodine is due to the mutual sharing of electrons, it is considered a covalent bond.
Thus, HI is a covalent compound.
Is HI polar covalent or nonpolar covalent?
In order to know whether HI is a polar covalent molecule or nonpolar covalent molecule, we have to check the electronegativity difference of the combining atoms.
If the electronegativity difference (ΔEN) is less than 0.4, then the bond is nonpolar covalent bond.
Now the electronegativity of Hydrogen and Iodine are mentioned below. (You can see the electronegativity of all the elements from this electronegativity chart).
- Electronegativity of Hydrogen (H) = 2.2
- Electronegativity of Iodine (I) = 2.66
So for HI, the electronegativity difference (ΔEN) = 2.66 – 2.2 = 0.46
This value lies between 0.4 to 1.7, which indicates that the bond between Hydrogen (H) and Iodine (I) is polar covalent bond.
Hence, HI is a polar covalent molecule.
I hope you have understood the reason why HI is a polar covalent compound.
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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