Question

What is the weakest intermolecular force?
(A) Hydrogen bonding
(B) Dispersion forces
(C) Ionic bonding
(D) Dipole-dipole

Answer 1

Hint: Intermolecular forces are those forces which hold a molecule together by means of attraction or repulsion force. The temporary attractive forces that result when the electrons in two adjacent atoms occupy positions to form temporary dipoles are the weakest.

Complete step-by-step answer:
The London dispersion force is the weakest intermolecular force as a temporary attractive force results in temporary dipoles in the molecules. This force is also known as induced dipole-induced dipole attraction. These attractive forces cause non-polar substances to condense to liquids and freeze to solids at low temperatures.
Because of constant motion of electrons, an atom or molecule can have a temporary dipole i.e. instantaneous, when its electrons are distributed unsymmetrically around the nucleus. This causes distortion in the neighbouring atom or molecule by the appearance. This results in an electrostatic attraction between the two atoms or molecules. For example. Fluorine molecules or noble gases.
While ionic bonding is the strongest as it is a permanent chemical connection between two atoms. And hydrogen bonding is also a strong dipole-dipole interaction between hydrogen atom and a highly electronegative atom.

Hence, the correct option is (B).

Note: The strength of London dispersion forces increases with polarizability. The interaction between two dipoles is expressed as its strength, $$\mu$$. It is directly proportional to the strength of the electric field. Vander Waal forces come under this category.