Determining Polarity

[AChoudhry_1L]

How do you determine if a molecule is polar? I know that you would look at the electronegativity, but is there a cut off between what counts as being electronegative enough to be considered polar?

[Wendy 1E]

In order to determine if a molecule is polar, you have to look at the shape and the differences in electronegativity. There is no cutoff in electronegativity. If the dipole moments all cancel, the molecule is nonpolar. If the dipole moments do not cancel, the molecule is polar.

[Chem_Mod]

There a few different cutoffs. Using the pauling scale of electronegativity (link below), generally we can say if the difference in electronegativity is about 0.5 or greater we can say it's a polar bond and the molecule may be polar. If it's greater than 1.5 - 2 or greater, it becomes ionic. However, it will vary from book to book. You do also have to consider shape as well, as dipoles may cancel depending on the shape.

https://en.wikipedia.org/wiki/Template: ... ling_scale)

[Leila_4G]

So, just to be sure, if it is a nonmetal + alkaline earth metal, it is polar molecule?

[Nare Nazaryan 1F]

Yes, the difference in electronegativity should be about 0.5 to be considered polar. Shape also plays a role in terms of the possibility of dipole moments canceling.

[Julieta Serobyan4D]

So, just to be sure, if it is a nonmetal + alkaline earth metal, it is polar molecule?

Yes, basically ionic bonds makes them polar