Polar and Non-polar bond

Jinghui Song 2J
Posts: 9
Joined: Wed Sep 21, 2016 2:59 pm

Polar and Non-polar bond

Hi

I am confused with how to decide which bonds are polar or non-polar, and how to decide which molecule is likely to be a polar or non-polar. Can anyone helps me out?

Marie_Bae_3M
Posts: 25
Joined: Wed Sep 21, 2016 2:57 pm

Re: Polar and Non-polar bond

I believe you can find whether a bond is polar or not by determining the difference in the electronegativities of the atoms being bonded. For example, Na-F is polar because Fluorine's electronegativity of 4.0 - Sodium's electronegativity of 0.93 = a huge polarity of 3.07.
To determine whether the polarity is large enough to become polar or not was set by rough guidelines. I'm not sure if this is accurate, but I think it was something like:
Polar: x>2.0
Polar-Covalent: 1.5<x<2.0
Non-polar: x<1.5
with x = to the difference between the electronegativities of the bonded atoms

Aaron_Trell_2J
Posts: 18
Joined: Sat Jul 09, 2016 3:00 am

Re: Polar and Non-polar bond

I believe you can also look at all of the dipole moments in a particular molecule and if all of these vectors cancel out then you have a non polar molecule and if they don't then you will have a polar molecule.

Arie Hakimi 1L
Posts: 25
Joined: Wed Sep 21, 2016 2:57 pm
Been upvoted: 2 times

Re: Polar and Non-polar bond

Do you guys know if we will have to memorize the exact electronegativity values for the main elements or can we just determine polarity by assuming trends in electronegativity to be true

Marie_Bae_3M
Posts: 25
Joined: Wed Sep 21, 2016 2:57 pm

Re: Polar and Non-polar bond

I don't think we have to know the exact values... just the general trend to find out which is more electronegative than the other. Also, the electronegativities given in the book are a bit different from the ones from my ap chem teacher and online so i dont think they'll be that specific as to finding the exact difference in electronegativity value without giving us the actual values of the atoms. But then again, I'm not really that sure.

PriscillaMariscal_3F
Posts: 21
Joined: Fri Jul 15, 2016 3:00 am

Re: Polar and Non-polar bond

If there is a linear molecule, and the dipole moments for the two outside atoms are facing towards the central atom, would the molecule be polar or nonpolar?

Janice Kim 3I
Posts: 33
Joined: Wed Sep 21, 2016 2:56 pm

Re: Polar and Non-polar bond

I usually draw out the lewis structure and determine from there. If the central atom of the lewis structure has all bonding pairs (ex. linear, trigonal planar, tetrahedral, etc.) and all atoms that are bonded to the central atom are the same, the molecule is non-polar because the equal and opposite dipole moments cancel out. When the atoms are different, there is a difference in electronegativity, thus creating a net dipole moment and making the molecule polar.

604744616
Posts: 34
Joined: Sun Jun 25, 2017 3:00 am

Re: Polar and Non-polar bond

With polar and non-polar bonds, I believe the easiest way to know the difference would be that polar bonds do not cancel and a non-polar must have zero electric dipole moment and bonds with dipoles must cancel. It is usually also easiest to draw out the lewis structure.

Xinye_Jiang_1A
Posts: 15
Joined: Sun Jun 25, 2017 3:00 am
Been upvoted: 1 time

Re: Polar and Non-polar bond

PriscillaMariscal_3F wrote:If there is a linear molecule, and the dipole moments for the two outside atoms are facing towards the central atom, would the molecule be polar or nonpolar?

non polar i think since they cancel.

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