Why hydrogen bonds are formed?

1 Answer

Hydrogen bonds occur where hydrogen is covalently bound to a strongly electronegative element, e.g. #"N", "O", "X"# #("X"# = halogen).

Explanation:

If hydrogen is bound to a strongly electronegative element, the electrons in the bond are polarized towards the electronegative element. We could therefore represent the polarized molecule as #"H"^(delta+)-"X"^(delta-)#.

The #"H"-"X"# molecule is thus polarized, it unequally shares its electrons. In the context of other similar molecules, this becomes an intermolecular force that is reflected in the elevated boiling points of #"H"_2"O"#, and #"H"-"F"#. This intermolecular force is the hydrogen-bonding interaction.