Like?

# London Dispersion Forces (Van Der Waal's Forces): Weak Intermolecular Forces

Start Your Free Trial To Continue Watching
As a member, you'll also get unlimited access to over 8,500 lessons in math, English, science, history, and more. Plus, get practice tests, quizzes, and personalized coaching to help you succeed.
Free 5-day trial
It only takes a minute. You can cancel at any time.
Start your free trial to take this quiz
As a premium member, you can take this quiz and also access over 8,500 fun and engaging lessons in math, English, science, history, and more. Get access today with a FREE trial!
Free 5-day trial
It only takes a minute to get started. You can cancel at any time.
1. 0:05 London Dispersion Force
2. 1:16 Weakness of Force
3. 2:01 Effects on Properties
4. 3:53 Lesson Summary
Share
Show Timeline

### Amy Meyers

Amy holds a Master of Science. She has taught science at the high school and college levels.

Learn how London dispersion forces are created and what effect they have on properties such as boiling and melting points. Discover this weak intermolecular force and how it is one of the van der Waals forces.

## London Dispersion Force

You know that every atom and molecule has electrons and that these electrons are in constant motion. At any one instant in time, these electrons can be more towards one side of a molecule than another. When the electrons are concentrated more at one end of a molecule, that end becomes slightly negative. The other end, where the electrons are not as concentrated, becomes slightly positive. At this instant, this molecule is a temporary dipole. This dipole can encourage a nearby molecule to also become dipole because the negative side of the first molecule will cause the electrons to run away on the other molecule (since negative (-) detests negative (-)).

Now these two adjacent dipoles created from the movement of electrons are attracted to each other. This very weak intermolecular force is called London dispersion force. London dispersion force is the weak intermolecular force that results from the motion of electrons that creates temporary dipoles in molecules. The London dispersion force is sometimes called a 'van der Waals force.' Van der Waals force is a general term that describes any attractive intermolecular force between molecules and includes both the London dispersion force and the dipole-dipole force discussed elsewhere.

## Weakness of Force

As you can imagine, this is an extremely weak force - much weaker than hydrogen bonding or any other intramolecular force. As I mentioned, this force works between all atoms and molecules. This is the only intermolecular force that works on noble gases and nonpolar molecules.

A London dispersion force works because of the movement of electrons. As you can imagine, the more electrons in the atoms, the stronger the force. Also, in a larger atom, the electrons are going to be filling the higher energy shells, which means they will be farther away from the nucleus and thus be less tightly held by the nucleus' attraction. The electrons farthest away are able to move more freely, creating a dipole easier. This is why the London force increases with increasing atomic mass.

## Unlock Content Over 8,500 lessons in all major subjects

Get FREE access for 5 days,
just create an account.

No obligation, cancel anytime.

Select a subject to preview related courses:

###### People are saying…

"This just saved me about \$2,000 and 1 year of my life." — Student

"I learned in 20 minutes what it took 3 months to learn in class." — Student

See more testimonials

Yes No

### What didn't you like?

What didn't you like?