Intermolecular Forces of Attraction - Forces of attraction that exist between molecules
The forces holding molecules together are generally called intermolecular forces.

there are "strong bonds" such as covalentor ionic bonds and "weak bonds" such as dipole-dipole interactions the London dispersion force and hydrogen bonding covalent bond〉 ionic bond 〉H bond 〉dipole-dipole forces ≈London forces





Dipole-Dipole Interactions are caused by permanent dipoles in molecules When one atom is covalently bonded to another with a significantly different electronegativities, the electronegative atom draws the electrons in the bond nearer to itself, becoming slightly negative. Intermediate dipole-dipole forces

Substances whose molecules have dipole moment have higher melting point or boiling point than those of similar molecular mass, but their molecules have no dipole moment.


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H-bonding

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Hydrogen bonds are a
caused by highly electronegative atoms. They only occur between hydrogen and oxygen, fluorine or nitrogen and are the strongest intermolecular force. The high electronegativities of F, O and N create highly polar bonds with hydrogen, which leads to strong bonding between hydrogen atoms on one molecule and the lone pairs of F, O or N atoms on adjacent molecules. The high boiling point of water is an effect of the extensive hydrogen bonding between the molecules:

  • Hydrogen bond
    Certain substances such as H2O, HF, NH3 form hydrogen bonds, and the formation of which affects properties (mp, bp, solubility) of substance. Other compounds containing OH and NH2 groups also form hydrogen bonds. Molecules of many organic compounds such as alcohols, acids, amines, and aminoacids contain these groups, and thus hydrogen bondingplays a important role in biological science.

London forces external image vdW.jpg

Weak London dispersion forces or van der Waal's force These forces alway operate in any substance. The force arisen from induced dipole and the interaction is weaker than the dipole-dipole interaction. In general, the heavier the molecule, the stronger the van der Waal's force of interaction., the boiling points of inert gases increase as their atomic masses increases due to stronger Landon dispersion interactions.



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  1. Covalent bonding

    It is mentioned here, because some solids are formed due to covalent bonding. . These solids are hard, brittle, and have high melting points. Covalent bonding holds atoms tighter than ionic attraction.


ionic bondexternal image halogen-ionic-bond.jpg

In ionic bonding, electrons are completely transferred from one atom to another. In the process of either losing or gaining negatively charged electrons, the reacting atoms form ions. The oppositely charged ions are attracted to each other by electrostatic forces, which are the basis of the ionic bond.
  • Ionic bonding is a type of electrostatic interaction between atoms which have a large electronegativity difference