How are intermolecular forces ordered from greatest to least?

When categorizing intermolecular forces based on their strength, we can arrange them from greatest to least as follows:

1. Ion-Ion Forces
2. Ion-Dipole Forces
3. Hydrogen Bonds
4. Dipole-Dipole Forces
5. Dipole-Induced Dipole Forces
6. Ion-Induced Dipole Forces
7. Dispersion Forces (London Forces)

Let’s break this down:

• Ion-Ion Forces: These are the strongest intermolecular forces, occurring between charged ions. The electrostatic attraction between oppositely charged ions creates a very strong force.
• Ion-Dipole Forces: These occur between an ion and a polar molecule. The charge of the ion interacts with the partial charges of the dipole, leading to significant attraction.
• Hydrogen Bonds: A special type of dipole-dipole interaction, hydrogen bonds occur when hydrogen is bonded to highly electronegative atoms like nitrogen, oxygen, or fluorine. This interaction is stronger than typical dipole-dipole interactions.
• Dipole-Dipole Forces: These forces exist between polar molecules, where the positive end of one molecule attracts the negative end of another.
• Dipole-Induced Dipole Forces: These are weaker interactions that occur when a polar molecule induces a dipole in a nonpolar molecule, causing temporary attractions.
• Ion-Induced Dipole Forces: Similar to dipole-induced forces but involve ions polarizing a neutral atom or molecule; these forces are generally weaker than dipole-induced interactions.
• Dispersion Forces (London Forces): The weakest of all dispersion forces are temporary induced dipoles that occur in all atoms and molecules due to the movement of electrons. These forces become significant when molecules are close together.

Understanding the relative strength of these forces helps in predicting the physical properties of substances, such as boiling and melting points.