van der Waals force

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A weak force of attraction between electrically neutral molecules that collide with or pass very close to each other. The van der Waals force is caused by the attraction between electron-rich regions of one molecule and electron-poor regions of another (the attraction between the molecules seen as electric dipoles). The attraction is much weaker than a chemical bond. Van der Waals forces are the intermolecular forces that cause molecules to cohere in liquid and solid states of matter, and are responsible for surface tension and capillary action.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


What is van der Waals force?

Van der Waals force is a weak attractive force between nonpolar atoms or molecules. It’s caused by one atom or molecule having a high concentration of electrons and another having a low concentration of electrons.

A molecule is polar if it has an uneven electrical charge, meaning it has a positively charged end and a negatively charged end. A nonpolar molecule does not have charged poles.

When the electrons of an atom are positioned so that one side of the atom has a larger group of electrons than the other, the atom temporarily becomes a dipole, meaning it has an end that is less negatively charged than the other.

This temporary dipole causes other atoms to be attracted to the less negative end of the atom. This attraction causes the other atoms’ electrons to group up and those atoms become dipoles as well. The result is a chain reaction of atoms becoming dipoles and attracting other atoms. The attractive force between these atoms is called van der Waals force.

As far as chemical bonds go, van der Waals force is among the weakest. Other types of bonds, such as covalent or ionic bonds, involve the actual sharing or exchanging of electrons rather than having them slowly gravitate toward each other.

Van der Waals force is responsible for surface tension and capillary action.

Why is van der Waals force important?

Van der Waals force is named for Dutch physicist Johannes Diderik van der Waals, who theorized that atoms must have some kind of intermolecular forces that attract them to each other. He based his theory on the fact that elements with different numbers of electrons have different boiling points and can even be at different phases of matter at room temperature.

Van der Waals force is the reason different elements have different boiling and melting points. The stronger the force between atoms, the more energy (heat) you need to break apart their bonds.

For example, iodine has a higher melting point than chlorine because iodine has more electrons than chlorine does. The more electrons an atom has, the more likely it can become a dipole and thus have a higher frequency of van der Waals force. In the case of iodine, the high instance of van der Waals force causes iodine to be a solid at room temperature, while chlorine is a gas at room temperature.

Did you know … ?

Van der Waals force occurs in every type of molecule, including polar molecules. However, polar molecules are able to form much stronger types of bonds due to their electrical charges.

What are real-life examples of van der Waals force?

This image gives a simple example of how van der Waals forces occur. You can see that the positioning of the electrons in the cloud leads to attractive force.

Van der Waals force is a force that bonds molecules together.


What other words are related to van der Waals forces?

Quiz yourself!

True or False?

A van der Waals force is the result of a concentration of protons in one atom being attracted by a low amount of protons in another.

How to use van der Waals force in a sentence