- Formed when two atoms in a bond have substantially different electronegativites
- The more electronegative atom attracts the electrons more, so it becomes slightly negative.
- The other atom in the bond becomes slightly positive due to the absence of electrons
- This forms a polar bond.
- This can then go on to attract other permanent dipoles, forming a permanent dipole - permanent dipole intermolecular bond.
- A dipole in a molecule could also induce a dipole in a neighbouring molecule.
- The delta negative part of the molecule repels the electrons on the neighbouring molecule away, so causing it to be slightly positive.
- The slightly positive end of one molecule and slighly negative end of the other molecule are then attracted towards each other.
- This forms a permanent dipole - induced dipole bond.
1 of 3
- Electrons in a molecule randomly move around the molecule.
- At one point they may be unevenly distributed - one side may be more concentrated with electrons than the other
- this causes that side to be slightly negative and the other side to be slightly positive.
- At this instant, this creates a dipole in the molecule
- This can then induce a dipole in a neighbouring molecule (the delta negative side repels electrons on the neighbouring molecule so making it slightly positive)
- These two molecules then attract each other, forming an instantaneous dipole - induced dipole bond.
- Larger atoms form stronger instantaneous dipole - induced dipole bonds
- They have more electrons so can create more positive/negative areas of charge
- The induced dipole is therefore also stronger
- This leads to greater attraction between the molecules, so take more energy to break.
2 of 3
- Forms when a hydrogen is attached to a small and electronegative N/O/F atom, which draws the bonding electrons towards itself (due to it's electronegativity), meaning it becomes quite negative (a high delta negative charge)
- This causes the hydrogen to become very positive.
- The delta positive hydrogen atom is then attracted to a lone pair on a delta negative N/O/F atom attached to a neighbouring molecule.
- Hydrogen bonding is the strongest type of intermolecular bonding (apart from giant covalent network/ionic lattice), and so molecules with hydrogen bonds will have high boiling points.
- Molecules which can form hydrogen bonds with water are usually soluble
- too few OH groups = cannot form enough hydrogen bonds to break the molecules apart
- too many OH groups = water cannot break so many hydrogen bonds apart so it is insoluble.
3 of 3