(a) Dipole-dipole
Many molecules are electric dipoles, that is, they have net positive charge on one part of the
molecule and net negative charge on another part. Since opposite charges attract and like charges
repel, these molecules will tend to orient themselves so that there is the most attraction and the
least repulsion.
Dipole-dipole attractions are effective over very short distances between molecules. This attraction
decreases sharply as the distance between adjacent molecules increases.
(b) Hydrogen Bonding
Strong dipole-dipole attractions occur in molecules containing hydrogen covalently bonded to a
nitrogen, oxygen or fluorine atom. The attraction occurs between the hydrogen covalently bonded
to a nitrogen, oxygen or fluorine in one molecule and the nitrogen, oxygen or fluorine on an
adjacent molecule. The covalent bonds within the molecules are quite polar due to the small sizes
of the atoms involved. The hydrogen in these covalent bonds has a partial positive charge, since
there are no inner core electrons and the shared electrons are strongly attracted to the small, very
electronegative atoms.The attractions that develop between these molecules are about four to five times stronger than other dipole-dipole attractions and are called hydrogen bonding. Hydrogen bonding is responsible for the unusual properties of water. The illustration below shows some of the hydrogen bonding.
sharon kalunda answered the question on
April 8, 2019 at 12:43