Intermolecular Forces

The forces that bond atoms together within a molecule are called intramolecular forces

The forces between atoms are intermolecular forces. They are weak attractions compared to the attraction between atoms and are easily broken by adding energy.

Intermolecular forces:

Ion dipole.

  • ionic with polar, cation with an anion

  • ionic substances dissolve easily in water (polar) by dissociating into ions

  • the force of attraction between ion and polar end is enough to overcome the force of attraction holding the ionic compound together

  • “ like dissolves like “ “ charged dissolves charged”

Dipole dipole

  • polar with polar

  • there is electrostatic attraction between oppositely charged ends of polar molecules

  • these forces usually occur in liquids

  • polar molecules will orient themselves so that the oppositely charged ends of the molecules are near to one another

a type of dipole dipole

hydrogen bonding

  • hydrogen in a molecule with O, N, or F - highly electronegative atoms

  • stronger than regular dipole dipole forces, but still weaker than ion dipole

  • the positive nucleus of hydrogen is attracted to the negative dipole of the neighboring molecule

induced dipole forces

  • dipole dipole

  • caused by the charge on one molcules causing a change in the distribution of electrons

  • inducing a dipole is a temporary polariziation

ion induced dipole forces

  • ion and non polar

  • results when an ion in close proximity to a nonpolar mlecule distorts the electron density of the non polar molecule

  • the molecule becomes momentarily polirized and the two molecules will be attracted

    to one another

dipole induced dipole forces

  • polar and non polar

  • the charge of a polar molecule is responsible for inducing the charge (by distortion of the electron cloud) on the nonpolar molecule

  • the molecule becomes momentarily polarized and the two molecules will be attracted to one anotheer

london dispersion forces

  • nonpolar and non polar

  • act between any particilies, but is the only force that acts between nonpolar molecules

  • occur for only an instant due to the molecules bonds vibrating and having a mometary, uneven distribution

  • molecules continue to do this on a random, ongoing basis

  • very short lived and extremely weak