Dispersion forces more commonly known as London dispersion forces(LDF) is a force acting between atoms and molecules since it is an intermolecular force. LDF is named after the German-American physicist Fritz London and is part of the van der Waals forces.
LDFs are exhibited by non-polar molecules because of the correlated movements of the electrons in interacting molecules. Because the electrons from different molecules start "feeling" and avoiding each other, electron density in a molecule becomes redistributed in proximity to another molecule. This is frequently described as formation of "instantaneous dipoles" that attract each other.
- Examples of molecules with LDF occurring between them are two:
- Hydrogen (H2) molecules
- Chlorine (Cl2) molecules
- Carbon dioxide (CO2) molecules
- Dinitrogen tetroxide (N2O4) molecules
- Methane (CH4) molecules.
- Below is a video that will explain the matter a little more clearly for you.
- Here are some diagrams that will also assist you in understanding LDF.
- How does LDF affect Boiling point and Melting point?
- What if the number of electrons and protons are the same?
So in conclusion the stronger the LDF the harder it is to break up the two molecules so the boiling point and melting point are higher. But in general the stronger the Intermolecular force the higher the boiling point and melting point, for LDF isn't the only intermolecular force that affects the boiling point and melting point.
- More information about LDF:
- London forces are present between all chemical groups and usually represent the main part of the total interaction force in condensed matter.
- LDF is the only attractive intermolecular force present between neutral atoms. Without LDFs, there would be no attractive force between noble gas atoms, and they wouldn't exist in liquid form.
- Due to the temporary nature of the dipoles which are the cause to LDFs, LDFs are the weakest intermolecular force, yet is the dominant force of attraction between identical non-polar molecules.
