Intermolecular forces Watch
Induced dipole - dipole interactions
Perminant dipole- dipole interactions
(in order of weakest to strongest)
1) London forces (induced dipole-dipole) exist between all molecules but are only really important between atoms (noble gases) or pure covalent molecules e.g. He or H2
Electrons are constantly moving which causes a temporary dipole in one molecule and this induces a dipole on a neighbouring molecule.
The more electrons there are in each molecule, the stronger the forces and the more energy needed to overcome them
2) Permanent dipole-dipole interactions occur between permanent dipoles in different molecules. The larger the difference in electronegativity, the larger the dipole and the stronger the attraction.
They occur between polar covalent molecules e.g. HCl
3) Hydrogen bonding is the attraction between the positive dipole on a hydrogen atom and the lone pair of electrons on a negative atom. H must be bonded to N, O or F
This is the strongest type of intermolecular force
(yes it has one plane of mirror symmetry, but that isn't enough)
Leave me alone to my wine-based stupor.
T'is still not enough.