Which is the weakest type of intermolecular force?
A. dipole-dipole
B. hydrogen bonding
C. ion-dipole
D. London dipersion force
The Correct Answer and Explanation is :
The correct answer is D. London dispersion force.
Explanation:
Intermolecular forces are the forces of attraction or repulsion that exist between molecules. These forces are responsible for the physical properties of substances, such as boiling point, melting point, and solubility. The strength of these forces varies, and the London dispersion force is the weakest of the commonly known types of intermolecular forces.
1. London Dispersion Force:
This force is also known as instantaneous dipole-induced dipole interactions. It arises due to the momentary fluctuations in electron distribution around atoms or molecules, which creates temporary dipoles. These temporary dipoles can induce dipoles in nearby molecules, leading to an attraction between them. London dispersion forces are present in all molecules, whether they are polar or nonpolar. However, they are the weakest because the dipoles they create are short-lived and relatively weak compared to other intermolecular forces. The strength of the London dispersion force increases with the size and mass of the molecules, as larger molecules have more electrons that can shift to create stronger temporary dipoles.
2. Dipole-Dipole Interactions:
Dipole-dipole interactions occur between polar molecules, where the positive end of one molecule is attracted to the negative end of another. This force is stronger than London dispersion forces because the dipoles are more stable and persistent, compared to the temporary dipoles in London dispersion forces.
3. Hydrogen Bonding:
Hydrogen bonding is a special type of dipole-dipole interaction that occurs when a hydrogen atom is bonded to a highly electronegative atom (like fluorine, oxygen, or nitrogen). This creates a particularly strong dipole, leading to a stronger attraction between molecules. Hydrogen bonding is much stronger than both dipole-dipole interactions and London dispersion forces.
4. Ion-Dipole Interactions:
Ion-dipole interactions are the strongest intermolecular force among the options listed. These occur when an ion interacts with the partial charge on the end of a polar molecule. The attraction between the ion and the dipole is very strong, significantly stronger than dipole-dipole and London dispersion forces.
In summary, London dispersion forces are the weakest type of intermolecular force because they arise from temporary fluctuations in electron distribution, making them less persistent and weaker compared to the other types.