Intermolecular Forces By Peter Demkowicz

Why? Intermolecular Forces

In simple, forces with which molecules attract each other.

Intermolecular Forces Properties Solids/Liquids Boiling/Melting Point Surface Tension Capillary Action Vapor Pressure Miscibility

Intermolecular Forces Hydrogen Bonds Dipole-Dipole interactions London Dispersion

Dipole-Dipole Molecules can have a separation of charge Molecules are attracted to each other in a compound by the valence electrons: Positive & Negative Stronger than London Dispersion

Orientation of Polar Molecules in a Solid

Dipole A polar molecule that has two poles.

Hydrogen Bonding Hydrogen bonding is the attraction between a hydrogen atom of a molecule to an unshared pair of electrons in another molecule. Hydrogen bonding occurs in molecules where hydrogen is covalently bonded to a very electronegative element. Hydrogen bonding occurs in molecules containing N, O, F.

Hydrogen Bonding, Continued Hydrogen bonds are the strongest of all intermolecular forces. Hydrogen bonds are responsible for the physical properties of many biological substances and, more importantly, water.

Hydrogen Interactions

Which of these are Hydrogen Bonds? H20 CH3F N2 H2CO

London Dispersion London forces are named after Fritz London (also called van der Waal forces) London forces are due to small dipoles that exist in non-polar molecules Since electrons are moving around in atoms there will be instants when the charge around an atom is not symmetrical The resulting tiny dipoles cause attractions between atoms/molecules

(London) Van der Waals Forces Dispersion (continued) Increase as the number of electrons increases. Weakest of all intermolecular forces.

Put the bonds in strongest order Ionic/covalent Dipole-Dipole London Dispersion Hydrogen Bonding

Which ones are Dipole, London Dispersion, and Hydrogen Bonding? C2H6 HCl CH3OH H2 H2O