London dispersion forces are the weakest type of intermolecular forces that exist between all atoms and molecules, whether polar or nonpolar. They arise due to temporary shifts in the distribution of electrons.
Key Points about London Dispersion Forces:
- Cause – At any moment, electrons in an atom or molecule may not be evenly distributed, creating a temporary dipole (slight positive and negative charges).
- Induced dipoles – This temporary dipole can induce a dipole in a neighboring atom/molecule, leading to a weak attraction between them.
- Universality – Present in all substances, but they are the only forces in nonpolar molecules (like noble gases, H₂, O₂, CH₄).
- Strength – Very weak compared to hydrogen bonds or dipole–dipole forces, but strength increases with:
- More electrons (higher atomic/molecular size) → stronger dispersion forces.
- Greater surface area → stronger attraction.
Example: I₂ (solid at room temperature) has stronger forces than F₂ (gas).
- Properties influenced – Affect boiling points, melting points, solubility, and physical state of nonpolar substances.