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Chemistry

Intermolecular Forces

Today we will learn about Intermolecular Force of attraction between any particle.

Before starting this topic, first thing that you should that the Forces we talking about here are not the ionic or covalent force between any atom of molecules but are weak Intermolecular Forces.

There are three types of IF:
  • London Forces or Dispersion Forces
  • Dipole-Dipole Forces
  • Dipole-Induced Dipole Forces

London Forces or Dispersion Forces

We known that atoms and molecules form bond to get stable. But even when they get stable, they can exert some Forces on other particles (other atoms and molecules). The particles which are neutral can also possess a momentary charge and in results become a temporary dipole. This results in the disturbance in the neighbouring particles and similarly the also possess momentary dipole. This results in the attraction of both the particles and this force of attraction is called London Force (named after a scientist) or Dispersion Forces. They are inversely proportional to the distance between the particles (1/r6).

They are very weak forces and they act in between the distance of 350 pm (pico meter).

Dipole-Dipole Forces

When the particles with some dipole come in interaction, they exert some attraction force between each other. This is called Dipole-Dipoles Forces. 
This force is strongest among all the three Forces. 
Similar Phenomenon happens here, but the charges are pregenerated which is not the case with LF.
They are also inversely proportional to distance between particle.( 1/r6)
The total force attraction force acting between any dipole dipole body increases as there is also London Force between these particles.
Hydrogen Bonding is an example of this type of force. 

Dipole-Induced Dipole Forces

The force of attraction between a body with dipoles and a neutral body is called as Dipole Induced Dipole Forces. 
The particles with dipole induces a temporary pole in the neighbouring neutral particles and they possess a force of attraction between each other. 
This force is also inversely proportional to distance between the two particles. 
The resultant force is increased because of the LF between them. 


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