Intermolecular Forces of Attraction

Intermolecular Forces of Attraction

Intermolecular forces of attraction are the forces of attraction that exist between molecules. Every molecule has some force of attraction when attached to another molecule. The three forces of attraction are: London Dispersion forces, Dipole-Dipole forces and Hydrogen Bonding.

London Dispersion Forces:
The force of attraction between any two molecules created by temporary dipoles which are caused by the movement of electrons both atoms.


Dipole Dipole Forces:
Electrostatic attraction caused by the positive end of one dipole being attracted to the negative end of another dipole.


Hydrogen Bonding:
Special case of dipole dipole attraction where a temporary covalent bond forms between hydrogen of one molecule and the oxygen, nitrogen or fluorine of an adjacent molecule.

All molecules attracted to another molecule have London Dispersion forces whether they be polar or nonpolar. However, the polarity of a molecule decides whether they have Dipole Dipole and/ or Hydrogen Bonding. If a pair of molecules are polar than they will have Dipole Dipole and possibly Hydrogen Bonding if there is an hydrogen on one molecule and an oxygen, nitrogen or fluorine on another molecule. But, if one molecule is nonpolar and the other is polar they will only have London Dispersion.

Hydrazine's Forces of Attraction:

N2H4 happens to have all three forces of attraction, London Dispersion, Dipole-Dipole, Hydrogen bonding:

Above is dash structure with the forces shown as well as some of the charges. As shown the slightly positive hydrogen is attracted to the slightly negative nitrogen. Both Hydrogen Bonding and Dipole Dipole forces occur between these two elements. The top bond shows the temporary covalent bond that forms and then breaks between the nitrogen and hydrogen. The bottom shows the attraction of a positive to a negative which just happens to also be the nitrogen and hydrogen. The London Dispersion forces, although there, can not be shown by any sort of symbol, they just occur randomly around the molecules.