Question

What is a London dispersion force?
(A) The weak intermolecular force that results from the motion of electrons that creates temporary dipoles in molecules.
(B) The strong intermolecular force that results from the motion of protons that creates temporary dipoles in molecules.
(C) The weak intermolecular force that results from the motion of protons that creates temporary dipoles in molecules.
(D) The intermolecular force that increases boiling points in molecules.
(E) The strong intermolecular force that results from the motion of electrons that creates temporary dipoles in molecules

Answer 1

Hint: The instantaneous dipole–induced dipole attractions are called London dispersion forces. It is the attraction that exists between two or more non- polar molecules. As these forces are generated because of the random motions of electrons on atoms within molecules, it is weaker as compared to other intermolecular forces.

Complete solution step by step:
- The intramolecular force of attraction is formed within a molecule, example of which are covalent bond, ionic bond and coordination bond.
-The forces of attraction between molecules which hold them together is called the intermolecular force of attraction. These forces are weaker than intramolecular forces.
-Intermolecular forces are responsible for the liquids, solids and solutions state of any compound.
-Some common types of intermolecular forces are London dispersion, dipole-dipole, Hydrogen bonding and ion-ion force.
-The unequal distribution of electrons about the nucleus in an atom can induce some dipole in the atom. When another atom or molecule comes in contact with this induced dipole, it can be distorted that leads to an electrostatic attraction between either atoms or molecules. London’s dispersion forces can be defined as a temporary attractive force due to the formation of temporary dipoles in a nonpolar molecule.
- London’s dispersion forces occur between all molecules.
The order of strength of these intermolecular forces is given below.
London’s dispersion force < dipole-dipole < H-bonding < Ion-ion
-So, we can say that London dispersion forces are the weakest intermolecular force. When the electrons in two adjacent atoms are displaced in such a way that atoms get some temporary dipoles, they attract each other through the London dispersion force.
-These intermolecular forces occur between non-polar substances. Due to these forces, they can condense to liquids and or freeze into solids at low temperature.

So, the correct option is (A) The weak intermolecular force that results from the motion of electrons that creates temporary dipoles in molecules.

Note: These London dispersion forces are found in the halogens (e.g., ${{F}_{2}}$ and ${{I}_{2}}$ ), the noble gases (e.g. Ne and Ar), and in other nonpolar molecules, such as carbon dioxide and methane.