Question

What are the strongest to weakest intermolecular forces?

Answer 1

1. Molecules are formed when atoms bond to each other, and these molecules interact with each other due to forces that act between them. These forces are known as intermolecular forces.
2. These forces help to determine which type of solvent they are soluble in, and their melting and boiling point.
3. There are four types of intermolecular forces - ion-dipole forces, hydrogen bonding, dipole-dipole forces, and Vander Waals forces.
4. Ion-dipole interactions are formed between an ion and a molecule having a dipole moment that is a polar molecule. Example: The interaction between $\mathrm{NaCl}$ and water, where water is a polar molecule and $\mathrm{NaCl}$is an ionic compound.
5. Hydrogen bonds are formed between the hydrogen atom of one molecule and the electronegative atom of another molecule. For example, hydrogen bonds are formed between water molecules, where the hydrogen of one molecule interacts with the oxygen of another water molecule.
6. Dipole-dipole forces are formed between polar molecules. Example: In $\mathrm{HCl}$a polar molecule, the interaction between the negative part ($\mathrm{Cl}$) with the positive part ($\mathrm{H}$) of another molecule of $\mathrm{HCl}$.
7. Vander Waals forces exist between not just the polar molecule but also the non-polar molecule.
8. Thus, among the following intermolecular forces, the strongest attraction exists between ion-dipole forces and the lowest is the Vander Waals forces. The strength of intermolecular forces of attraction depends on the electrostatic forces of attraction between the charges, which can be fully or partially charged, induced dipoles or permanent dipoles, etc.
9. Ion-dipole interactions are much stronger than others as the ions have a full charge on them while dipoles have a partial charge on them. Thus, ions tend to form strong interactions with others. Hence, these have electrostatic forces of attraction between fully charged ions and partially charged dipoles.
10. Vander Waals's forces of attraction are the weakest as it is not formed among charged molecules but rather among molecules that have a temporarily induced dipole. These types of interactions are found to be short-lived, weak, and short-ranged.
11. The order of strength in the decreasing order is: ion-dipole, hydrogen bonds, dipole-dipole, and Vander Waals Forces.