Maharashtra BoardEnglish MediumSTD 12 ScienceChemistrySolid State3 Marks
Question
What are intermolecular forces of attraction involved in molecular crystals ?
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Answer
The intermolecular forces involved in molecular crystals are as follows: (1) Weak dipole-dipole interactions : The solids constituting polar molecules like $HCl , H _2 O , SO _2$, etc. which possess permanent dipole moment involve weak dipole-dipole interactions.
(2) Very weak dispersion or London forces : The solids consisting of nonpolar molecules like $CH _4, H _2$, etc. involve weak dispersion forces. They are also involved in monoatomic solids like $Ar , Ne$.
(3) Intermolecular Hydrogen bonds :
In this crystalline solids, the constituent particles are the molecules which contain hydrogen atom linked to highly electronegative atom like F, O or N.
In these, molecules are held by hydrogen bonds in which H atom of one molecule is bonded to electronegative atom (like F, N or O) of another molecule.
Since hydrogen bonding is weak, these solids have very low melting points and generally at room temperature they exist in the liquid or gaseous state.
They are non-conductors of electricity.
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