These hold molecules together and are very weak; there are three types of these forces…
1. Instantaneous Dipole – Induced Dipole (London Forces) à Weakest of the three
2. Permanent Dipole – Permanent Dipole interactions
3. Hydrogen Bonding (strongest of the three)
London forces act between all atoms and molecules à electrons in charge clouds move quickly, more one sided creates temporary dipoles which creates chain reaction of temporary dipoles (domino effect). The dipoles are constantly created/destroyed so move, overall attraction between atoms or molecules.
Stronger London forces = higher mpt and bpt
· Liquids with stronger LFs have higher bpts as more energy needed to overcome forces
Solids melting also have higher mpt if stronger forces alkanes…