1) Induced Diplole-Dipole (van der waals)
Caused by the temporary movement of electrons - foundb between all atoms and molecules.
- At any moment, electrons are more likely to be on one side than the other - this dipole can induce another temporary dipole in the opposite direction on a neighbouring atom.
- Larger molecule = more electrons, large dipole, therefore high m.p and b.p.
2) Permenant Dipole-Dipole
Slightly negative and slightly positive atoms cause weak electrostatic forces of attraction between molecules - found in polar molecules.
3) Hydrogen Bonding
Can only happen when hydrogen is covalently bonded to a lone pair on oxygen, fluorine or nitrogen.
- H has a high electron density, O, F and N are very electronegative so bond is polarised.
- High b.p and m.p, ice is less dense.
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