TUESDAY REVIEW SESSIONOCTOBER 4 , 2010

Intermolecular Forces and Solubility

Intermolecular Forces

Definition: Forces between moleculesIntermolecular forces are much

weaker than intramolecular forces

There are three different typesLondon Dispersion Forces/ Van der

WaalsDipole-Dipole InteractionsHydrogen Bonds

London Dispersion Forces

Also referred to as Van der Waals forces

Occurs because of momentary dipole (uneven distributions of electrons in a molecule causing a partially negative end and a partially positive end)

These are the weakest intermolecular forces

Dipole-Dipole Interactions

Occurs when polar molecules align so that their oppositely charged ends are attract each other

This bond is stronger than Van der Waals forces

Hydrogen Bonding

A type of dipole-dipole bond that occurs when hydrogen is bonded to a highly electronegative atom (O, F, N)

This is the strongest intermolecular force

Intermolecular Forces Trends

Compounds with stronger intermolecular forces will be harder to separate therefore they will have larger melting points and boiling pointsThis means compounds with weak

intermolecular forces are more likely to be found in gaseous form, while compounds with stronger molecular forces are more likely to be found as liquids or solids