Determining Whether a Compound is Ionic or Molecular

Electronegativity difference (ΔEN) is the difference in the electronegativities of two bonded atoms or ions.

Types of Bonds are determined on the ΔEN

0-0.4 is Nonpolar Covalent

0.5-1.7 Polar Covalent

1.7 is Ionic

Non-Polar Covalent Bonds

The bonding electrons are in the middle between the 2 chlorine atoms due to their equal pulling of the electrons. 

All diatomic molecules are non-polar covelent  (equal electronegativities)

Small Differences in EN will result in the bond being NPC as well

Polar Covalent Bonds

The Bonding electrons are closer to atom with the higher electronegativity.  

In this case the hydrogen end would be slightly positive and the chlorine end would be slightly negative

Summary