what are london and dipole-dipole forces???

Dispersion Forces or London Forces are the forces of attraction between two temporary dipoles It occur between atoms or non-polar molecules.

Atoms or non-polar molecules have no dipole moment as they are electrically symmetrical. However, for some reason, momentarily an atom or non-polar molecule becomes electrically unsymmetrical. As a result, instantaneous dipole is developed on that atom for a very short time. This instantaneous dipole induces dipole on another atom close to it.

 

Dipole-Dipole interaction or Dipole-Dipole Forces

* Forces between molecules possessing permanent dipole

* Increase with decrease in distance

* For stationary polar molecules, Eāˆ 1/r3

* And for rotating polar molecules, E āˆ 1/r6

Where, E = Interaction energy and r = Distance between the polar molecules

* For polar molecules, total intermolecular forces = Dipole-dipole forces + London forces

* Dipole-dipole interaction between two HCl molecules:

 
 


 

  • 1

When two atoms are bonded together, then one atom having higher electronegativity value like F gets partial negative charge and other like H gets partial positive charge. This results in a molecules of separated charge called polar molecule or dipole. For example HF.

Dipole-dipole forces occurs between permanent dipole. Dipole molecule has partial positive and partial negative charge. So, positive charge of one dipole interact with negative charge of other dipole and vice versa resulting dipole- dipole force. These molecules also interact by weak London force or dispersive force. Hence, polar molecules are interacted by total of dipole-dipole force and London force.

  • 3

when 2 or more atom are bonded together though 1 atom have high electronegativity whichgets -ve charge &other like H gets partially +ve charge known as polar molecule . and this force of attaraction was found by 1st in london so, it is also called london force

  • -1

dipole dipole forces are the weak intermolecular forces  due to which atoms held togethr. like hydrogen bonded molecular solids in which hydrogen attached wih O,N,F.

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