My chemistry teacher told me that chemical bonds are of two types: intramolecular and intermolecular. He said that intermolecular forces come under the category of intermolecular chemical bond.

I have never read such statement anywhere. Nor can I find anything on the Internet that would support this statement.

My understanding is that chemical bond is a force that holds atoms together in a chemical species. Since intermolecular forces do not hold atoms together, they should not be termed as chemical bond.

So, are intermolecular forces a type of chemical bond?


1 Answer 1


The IUPAC definition of "chemical bond" is:

When forces acting between two atoms or groups of atoms lead to the formation of a stable independent molecular entity, a chemical bond is considered to exist between these atoms or groups. The principal characteristic of a bond in a molecule is the existence of a region between the nuclei of constant potential contours that allows the potential energy to improve substantially by atomic contraction at the expense of only a small increase in kinetic energy. Not only directed covalent bonds characteristic of organic compounds, but also bonds such as those existing between sodium cations and chloride anions in a crystal of sodium chloride or the bonds binding aluminium to six molecules of water in its environment, and even weak bonds that link two molecules of $\ce{O_2}$ into $\ce{O_4}$, are to be attributed to chemical bonds.

So the answer is "yes" in some cases.

See also the IUPAC definition of "molecule":

... must correspond to a depression on the potential energy surface that is deep enough to confine at least one vibrational state

So, for example, a water-water dimer, held together by hydrogen bonding, has a monomer-monomer potential energy surface that is deep enough to confine at least one vibrational state, and it would be appropriate to refer to the hydrogen bond as a chemical bond.

  • 1
    $\begingroup$ But if we ignore the last sentence for a moment, the whole definition indicates that intermolecular forces should not be considered as chemical bond. Phrases such as 'stable independent molecular entity' and 'existence of a region between nuclei...' make an image that chemical bonding is an intramolecular phenomenon. Anyway, the last sentence sidelines all this and makes it clear that intermolecular forces are indeed chemical bond. $\endgroup$ Feb 26, 2018 at 15:47
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    $\begingroup$ @AumkaarPranavShukla for IUPAC, once the force is enough to confine at least one vibrational state, the definition of "molecule" is met. For example, a water dimer, held together by hydrogen bonding, has monomer-monomer vibrational states, so it is considered a stable independent molecular entity. $\endgroup$
    – DavePhD
    Feb 26, 2018 at 15:56

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