How does electronegativity impact polarity of molecules?

2 Answers
Mar 19, 2014

Electronegativity is the measure of the ability of an atom to attract electrons to itself. Fluorine is the most electronegative element and francium is one of the least electronegative.

Atoms that are high in EN tend to take electrons and atoms low in EN tend to give up electrons. So, higher electronegativity helps atoms take more control over shared electrons creating partial negative regions and partial positive regions which result in dipoles that cause polarity.

The molecule's polarity will be determined on the negative and positive regions on the outer atoms in the molecule.

Mar 19, 2014

Differences in electronegativity between two atoms can cause the polarization of the bond that connects them, but the overall polarity of a molecule also depends on the relative orientations of the bonds.

For example, #H_2# has two atoms that have the same electronegativity so it is non-polar, but #HF# is polar because the electrons are attracted to #F# more than to #H#.

In #CF_4# each of the four #C-F# bonds is polarized because #F# is more electronegative than #C#, but the four bonds are symmetrically opposed to each other (pointed at the vertices of a regular tetrahedron), so that the polarity of the bonds exactly cancels out, and the molecule as a whole is non-polar.