Polarity of Molecules

Polarity of Molecules

 

The two factors that determine the polarity of molecules. These are:

1) The polarity of the bonds between atoms which can be studied based on electronegativity, and

2) The geometrical shape of the molecule which can be predicted via the valence shell electron

pair repulsion (VSEPR) theory.

Bond Polarity

Electronegativity (EN) - Measure of the relative tendency of an atom to attract electrons to itself

when chemically combined with another atom. The higher the value of electronegativity, the more it tends to attract electrons toward itself.

Polar covalent and Non-polar covalent bonds

Polar covalent bonds occur when electron pairs are unequally shared. The difference in

electronegativity between atoms is significant. 

The separation of charges makes the bond polar. It creates an electric dipole. Dipole refers to “two poles,” meaning there is a positive and a negative pole within a molecule. Elements with the higher EN value become the partial negative pole while elements with the lower EN value become the partial positive pole. This makes the molecule a polar molecule

Non-polar covalent bonds occur when electron pairs are shared equally or the difference in electronegativity between atoms is less than 0.5.