Van der Waals forces: The sum of the attractive or repulsive forces caused by intermolecular forces. Induced dipole: A dipole formed in a non-polar molecule caused by an adjacent molecule which has an instantaneous dipole. Instantaneous dipole: A dipole which forms in a non-polar molecule due to the sudden, temporary, uneven distribution of electrons. Induced dipoles occur when there is a temporary uneven distribution of electrons in a non-polar molecule causing repulsion or attraction in an adjacent molecule.ĭipole: Occurs within a molecule when two atoms in a covalent bond have different affinities for electrons (electronegativities), so the ‘push and pull’ of their shared electrons results in one atom maintaining most of the electron density and a partial negative charge, leaving the other atom with a partial positive charge.London dispersion forces are the weakest intermolecular forces arising from induced instantaneous dipoles.

These interactions are known as London dispersion forces, and are considered part of the van der Waals forces or weak intermolecular attractions. These instantaneous dipoles can cause dipoles to form in adjacent molecules by repelling and attracting them with electrostatic interactions. However, sometimes this even distribution can be affected by an adjacent molecule which may causes the distribution to become temporarily uneven, this creates an instantaneous dipole, and the molecule now has partial positive and negative charges (see below). fluctuations in molecules (known as London forces, or dispersion forces) are present even between permanently polar molecules and produce, generally. Non-polar molecules have an even distribution of electrons due to their atoms having very similar or the same electronegativities. London Dispersion Forces are the weakest intermolecular force and exist when a temporary dipole forms in a non-polar molecule, creating an induced dipole in an adjacent molecule.

London dispersio forces