Intermolecular forces 2

• Solid


  - Fixed shape

  - Fixed volume

  - Does not flow
• Liquid


  - NO fixed shape

  - Fixed volume

  - Incompressible

  - Flow readily
• Gas


  - No fixed shape

  - NO fixed volume

  - Compressible

  - Flows readily
• Intermolecular forces


  - IMFs are generally much weaker than forces between atoms (intramolecular forces)

  - An IMF can produce an intermolecular potential energy

  - IMFs explain why substances take on the properties of solids, liquids or a gas under standard temperature and pressure

  
• Intramolecular Forces


  - Generally much stronger than IMFs

  - An intramolecular force will produce intramolecular potential energy

  - An intramolecular force is covalent, ionic or metallic bond

  --> Forces that keep molecules together

  
• Ion-dipole forces


  They are important in solutions

  
• Dispersion forces (london dispersion forces)

  - Motion of electrons that create a dipole

  - Weakest IMF notice in nonpolar molecule

  
• Polarizability


  Squashiness of electron cloud

  - The more electrons the more polarizable
• Dipole-dipole forces


  - Polar molecules

  - Permanent dipole, the positive end is attracted to the negative of it's neighbor

  - Have short range

  - stronger than dispersion

  
• Strength og Dipole-Dipole forces

  - How polar is the molecule?

  - Bigger the difference in electronegativity more polar molecule stronger d-d force.
• Hydrogen bonding


  - H must be attracted to highly EN atom (usually F O N)

  - Nearby neighboring molecule must have highly EN atom with a lone pair of electrons

  - Have to be bonded to H

  
• Ion-Dipole Forces


  Observed when you have an ion in a polar solvent

  - Have to be polar

  
• Dispersion Forces (London Dispersion Forces)


  - Motion of electrons that create a dipole

  - Weakest IMF in non-polar molecule

  
• Molecular shape


  Linear molecules have higher surface area so more contact and stronger dispersion forces.