OH- ion is a POLAR ion.
But why?
And how can you say that OH- ion is a polar ion?
Want to know the reason?
Let’s dive into it!
OH- ion is a POLAR ion because any two bonding atoms whose electronegativity difference is between 0.4 to 2.0 forms a polar bond.
Here in OH- ion, the electronegativity difference of Oxygen atom (O = 3.44) and Hydrogen atom (H = 2.2) is 1.24 (i.e 3.44 – 2.2 = 1.24). This value (1.24) is between 0.4 and 2.0, hence the OH- ion is a polar ion.
Didn’t understand what is written above?
Let me explain this in a short and simple way (with 3D images).
Why is OH- a Polar ion? (Explained!)
OH- ion is a polar ion because it has a partial positive charge (ẟ+) on the Hydrogen atom and partial negative charge (ẟ-) on the Oxygen atom.
In short, the OH- ion forms a pole of positive charge and negative charge on it. Hence OH- ion is a polar ion.
But wait, let me give you some detailed information about the polarity of OH- ion.
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 OH- ion.
You can see the electronegativity values of Oxygen (O) and Hydrogen (H) atoms from the periodic table given below.
From the above image;
So for OH- ion, the electronegativity difference (ΔEN) = 3.44 – 2.2 = 1.24
This value lies between 0.4 to 1.7, which indicates that the bond between Oxygen (O) and Hydrogen (H) is polar covalent bond.
Hence, the OH- ion is a polar ion.
How does an OH- ion become a Polar ion?
In an OH- ion, there is one oxygen atom (O) and one hydrogen atom (O). Both these atoms are covalently bonded with each other by sharing one electron pair between them.
If we compare the electronegativity of oxygen and hydrogen, then oxygen is more electronegative than hydrogen.
This means that the oxygen atom has more tendency to attract the shared electron pair towards itself.
As the electron pair remains attracted towards the oxygen atom, the partial negative charge (ẟ-) appears on the Oxygen atom (O) and partial positive charge (ẟ+) appears on the Hydrogen atom (H).
In this way the partial positive and partial negative charges are generated on the OH- ion and hence OH- ion becomes a polar ion.
I hope you have understood the reason behind the polarity of OH- ion.
See the polarity of other molecules to make your concepts clear:
Is SeF6 Polar or Nonpolar?
Is ICl3 Polar or Nonpolar?
Is XeO3 Polar or Nonpolar?
Is XeO4 Polar or Nonpolar?
Is POCl3 Polar or Nonpolar?
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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