Question

Why hydrogen bonds are formed?

Answer 1

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.