8.4 Attractive Forces part 2 – cont.

Weaker Forces of Attraction• Weaker forces are temporary attractions that

exist between neighboring particles due to temporary or permanent partial charges (+ or -) on the particles. The attractions are usually indicated in diagrams using dashed lines. -------

• Attractions also vary in strength, depending upon the identity of the substances involved, and this strength is indicated by how much energy is required to break the bond.

Weaker Forces of Attraction

Weaker Forces of Attraction• Since an ion is involved in the ion-dipole

interaction, these attractive forces tend to be stronger. It can take from 40-600 kJ/mol to break these bonds.

Weaker Forces of Attraction• In dipole-dipole

interactions, these attractive forces are significantly weaker due to only partial charges being involved.

Weaker Forces of Attraction• They require

only 5-25 kJ/mol to break these attractions between neighboring particles.

• The amount depends upon the size of the partial charges.

Weaker Forces of Attraction• Hydrogen

bonding is another one of the weaker forces of attraction that can exist between particles. It takes from 10-40 kJ/mol to break these bonds.

Hydrogen Bonding.flv

Weaker Forces of Attraction• One of the most common substances that

forms hydrogen bonds is water: molecular_dance_of_water's_hydrogen_bonds.flv

Weaker Forces of Attraction• The weakest

force of attraction that can occur between particles in a substance involves induced dipoles.

Weaker Forces of Attraction• Induced dipoles can

exist in atomic substances (like xenon) in addition to molecules. Larger atoms or molecules can have larger induced dipoles due to the presence of more electrons.

Weaker Forces of Attraction• The forces attracting induced dipoles are

referred to as London dispersion forces, and can require between 0.05-40 kJ/mol to break.

Weaker Forces of Attraction• London dispersion forces are weaker forces

because induced dipoles are temporary; they don’t exist for long, but may reform quickly.

References:• http://www.chem.purdue.edu/gchelp/liquids/character.html• http://www.chem.wisc.edu/~newtrad/CurrRef/BDGTopic/lab/Crystlab2.GIF• http://lgfl.skoool.co.uk/uploadedImages/coord11.2_covalentbonding2_v2.gif• http://www.dur.ac.uk/p.m.johnson/electric_circuits/images/dia_atom_cores.gif• http://www.chemistry.wustl.edu/~courses/genchem/Tutorials/Water/images/nacl.jpg• http://web.arc.losrios.edu/~borougt/DiamondStructure.jpg• http://www.oocities.org/rjwarren_stm/PolarityOHbond.jpg• http://www4.nau.edu/meteorite/Meteorite/Images/HydrogenBond.jpg• http://cost.georgiasouthern.edu/chemistry/general/molecule/polar.htm• http://virtual.yosemite.cc.ca.us/webbg/chem101/ch11lecture/intermolecforces.htm• http://www.grandinetti.org/resources/Teaching/Chem121/Lectures/BondPolarity/ColvanttoIonic.gif• http://www.drkstreet.com/resources/metallic-bonding-animation.swf• http://www.chem.ufl.edu/~itl/2045/matter/FG11_002.GIF• http://mysite.verizon.net/kdrews47/interactions/ldf.gif• http://www.colorado.edu/physics/2000/applets/h2ob.html• http://antoine.frostburg.edu/chem/senese/101/liquids/faq/h-bonding-vs-london-forces.shtml• http://cost.georgiasouthern.edu/chemistry/general/molecule/forces.htm• http://www.bbc.co.uk/scotland/learning/bitesize/higher/chemistry/images/bonding_fig11.gif• http://www.northland.cc.mn.us/biology/Biology1111/animations/hydrogenbonds.html• http://www.chem.purdue.edu/gchelp/liquids/ioninddp.gif• http://chemwiki.ucdavis.edu/@api/deki/files/3831/=160inducedipole.gif

References - Videos:• http://www.youtube.com/watch?v=QqjcCvzWwww• http://www.youtube.com/watch?v=LKAjTE7B2x0&NR=1• http://www.youtube.com/watch?v=LGwyBeuVjhV• http://www.youtube.com/watch?v=cThvGD-o_90