Molecular Polarity
- To determine whether a molecule with more than two atoms is polar, the following things have to be taken into consideration:
- The polarity of each bond within the molecule
- How the bonds are arranged in the molecule (i.e the geometry of the molecule)
- Some molecules have polar bonds but are overall not polar because the polar bonds in the molecule are arranged in such way that the individual dipole moments cancel each other out
A polar molecule
There are four polar covalent bonds in CH3Cl which do not cancel each other out causing CH3Cl to be a polar molecule; the overall dipole is towards the electronegative chlorine atom
A nonpolar molecule
Though CCl4 has four polar covalent bonds, the individual dipole moments cancel each other out causing CCl4 to be a nonpolar molecule
Exam Tip
When the pulls of the atoms are not equal and opposite, there is a net pull so the molecule is polar.