However, although a molecule like CHCl 3 has a tetrahedral geometry, the atoms bonded to carbon are not identical. In contrast, \(CHCl_3\) is a polar molecule (right panel in figure above).
The whole of the outside of the molecule is somewhat negative, but there is no overall separation of charge from top to bottom, or from left to right. For example, carbon dioxide has two polar CO bonds, however, their dipole moments, being at 180 o, are canceled, and therefore, the molecule has no net dipole and is nonpolar: If the dipole moments are of different magnitudes but in opposite directions, then the net dipole moment will be the vector sum (subtraction) of these dipole moments. The electronegative chlorine draws electrons towards itself.Ĭonsider \(CCl_4\), (left panel in figure below), which as a molecule is not polar - in the sense that it doesn't have an end (or a side) which is slightly negative and one which is slightly positive. The manner in which the individual bonds contribute to the dipole moment of the molecule is nicely illustrated by the series of chloromethanes shown below. Using the equation above, the dipole moment is calculated to be 1.85 D by multiplying the distance between the oxygen and hydrogen atoms by the charge difference between them and then finding the components of each that point in the direction of the net dipole moment (the angle of the molecule is 104.5). In more complex molecules with more than one polar covalent bonds, the three-dimensional geometry and the compound’s symmetry determine whether the molecule has a net dipole moment.
