Understand the dipole moment in chemistry

Dipole moment and chemical compounds

In the chemistry, you have to assume that basically every chemical bond has a dipole moment, provided it consists of different substances. To understand this, you need to keep the following in mind:

• Each atom consists of an atomic nucleus and an atomic shell. The atomic shell is always negatively charged because it consists of negative electrons. You know that from your chemistry class.
• Two atoms combine with each other that have different numbers of electrons, for example Hydrogen and chlorine, one part of the resulting molecule has more negative charges in the shell than that other. That leads to the dipole moment.
• Since the electrons form pairs, you must assume that the electron prefers the hydrogen single electron of chlorine is to be found, because the atomic nucleus of chlorine is positively charged than that of the Hydrogen. The well-known picture of H.
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  ⁺ and Cl^-. Whereby the element remains bound due to the electrical attraction. It has the dipole element on the outside. The larger an atomic nucleus, the more positive charge it has, which leads to the effect that large nuclei attract the electrons of the small atoms towards them.
• Even if the atom has an electrically polar bond and thus has a dipole element, the connection as a whole cannot have a dipole element to the outside. Simply because the dipoles cancel each other out. This is usually the case with carbon compounds because the arrangement of the atoms in the molecule cancels the dipole moment as a whole.


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• The arrangement of the atoms always plays a role. When connecting water H₂O it is very important that the atoms are not arranged in a row, but at a bond angle of 105 ° If the atoms were at 180 ° -angle arranged, the substance would not have a dipole element to the outside.

Meaning of the dipole moment

• The dipole moment causes molecules to stick together, for example substances which, at room temperature, should actually be gaseous with the size of their molecules, appear as liquids. This is the case, for example, with water, which has a boiling temperature of 100 ° C because of the dipole moment. That is the reason why methane has a gaseous state of aggregation at room temperature and water a liquid one.
• The dipole moment is also important for the solubility of substances. The dipole of the water makes it a good solvent for many salts, which also usually have a dipole moment.

The explanations are kept somewhat general, so that you can more easily understand the concept of the dipole moment in principle. Of course, in chemistry, substance formation is more complex overall.