Intermolecular forces

• London dispersion forces

  Weak forces present between non-polar covalent molecules.

  When the electron distribution becomes concentrated more on one side then one end becomes more negative and more positive. This causes a temporary dipole which disturbs the electrons in a nearby molecule, repelling the electrons and inducing a dipole in that molecule.

  The temporary dipole and the induced dipole attract each other and pull the molecules together.
• Dipole-Dipole forces


  Permanent forces present between polar molecules because they have a permanent positive and negative end which attract each other. They are slightly stronger than London dispersion forces.
• Hydrogen bonding

  Strongest intermolecular force. Hydrogen bonds form when compounds have hydrogen directly bonded to fluorine, oxygen, nitrogen. When two of these molecules are close together, there will be an attraction between the positive end of one and the lone pair of electrons on the other.
• Intermolecular forces

  Intermolecular forces are the attractions or interactions between molecules that hold them together