# What determines the polarity of a molecule?

Possibly the indication of this is the relative polarity of $\text{chloroform}$, $C H C {l}_{3}$, versus $\text{carbon tetrachloride}$, ${\text{CCl}}_{4}$. Both molecules have ""^(+delta)C-Cl^(delta-) bonds, which are reasonably polar.
If we sum up the individual bond dipoles, however, ${\text{CCl}}_{4}$ sums TO ZERO, and thus has ZERO DIPOLE MOMENT - if you don't see this consider vector addition with very symmetrical tetrahedral bond angles. Because the 1xx""^(-delta)C-H^(delta+) and 3xx""^(+delta)C-Cl^(delta-) bond dipoles in chloroform do not sum to ZERO, the molecule has a resultant dipole moment. ""^(+delta)H-Cl^(delta-), and ""^(-delta)OH_2^(delta+) are polar molecules by this same reasoning.