States of Matter — Chemistry STD 11 Science — Question
Maharashtra BoardEnglish MediumSTD 11 ScienceChemistryStates of Matter6 Marks
Question
Explain briefly London dispersion forces.
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Answer
London dispersion forces:
In nonpolar molecules and inert gases, only dispersion forces exist.
Dispersion forces are also called as London forces or van der Waals forces.
It is the weakest intermolecular force that develops due to interaction between two nonpolar molecules.
In general, all atoms and molecules experience London dispersion forces, which result from the motion of electrons.
At any given instant of time, the electron distribution in an atom may be asymmetrical, giving the atom a short$-$lived dipole moment. This momentary dipole on one atom can affect the electron distribution in the neighbouring atoms and induce momentary dipoles in them. As a result, weak attractive force develops.
For example, substances composed of molecules such as $O_2, CO_2, N_2,$ halogens, methane gas, helium and other noble gases show van der Waals force of attraction.
The strength of London forces increases with increase in molecular size, molecular mass and number of electrons present in an atom or molecule.
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