On the other hand, if the molecule has a very symmetric structure or if the polarities
of different bonds cancel each other, the molecule as a whole may be nonpolar, even
though the individual bonds are quite polar. Tetrahedral molecules such as CH4 and
CC14 and trigonal molecules and ions such as SO3, NO3-, and ~03a~re -all nonpolar.
The C - H bond has very little polarity, but the bonds in the other molecules and ions
are quite polar. In all these cases, the sum of all the polar bonds is zero because of the
symmetry of the molecules, as shown in Figure 3-18.
Nonpolar molecules, whether they have polar bonds or not, still have intermolecular
attractive forces acting on them. Small fluctuations in the electron density in such