Intermolecular Forces

London Dispersion Forces (LD)

  • Also called “Induced Dipole“ Forces

  • Occurs when the electrons of one molecule attract the nuclei of another molecule

  • Relatively weak force, but the cumulative effect can be massive

  • The greater the atom or molecule, the greater the LD force

    • because there are more protons and electrons and therefore a larger attractive force

  • The more compact or linear a molecule, the closer the molecule can fit next to others, causing a greater LD force:

Pentane and Isopentane (isomers) example
Pentane Structural Diagram

Pentane has a boiling point of 36°C, and is linear (allowing a better stacking ability)

Isopentane has a boiling point of 28°C (doesn’t stack as well