How does a molecules symmetry relate to polarity?

1 Answer
Nov 23, 2015

Answer:

Polarity results from the vector sum of the individual bond dipoles. Clearly, molecular symmetry determines the vector sum

Explanation:

Take 2 molecules, #CF_4#, and #CHCl_3#. Both #C-Cl#, and #C-F# bonds are quite polar (the halogen is more electronegative than carbon, and the halogen atom polarizes electron density towards itself. Now, #F# is more effective than #Cl# in this activity. Nevertheless, #CF_4# is non-polar, whereas chloroform is quite polar as solvents go. Why?

Molecular polarity results from the vector sum of the individual bond dipoles. When the #CrarrF# dipoles are added, the overall vector sum is zero (necessarily, because #CF_4# is a regular tetrahedron. When the #CrarrCl# and the #C-H# dipoles are added, the resultant is non-zero.