UNIT 10

• Types of Forces in between molecules:

  1. London dispersion Forces
  2. Dipole-dipole forces
  3. Hydrogen bonding
  4. Ion-dipole forces
• London dispersion forces - Present in all molecules
• London dispersion -

  • Halogens: fluorine (F2), chlorine (Cl2), bromine (Br2), and iodine (I2)
  • Nobel gases: helium (He), neon (Ne), argon (Ar), and krypton (Kr)
•  Dipole-dipole - present in polar molecules
• Dipole-dipole -

  • Hydrogen chloride (HCl), hydrogen fluoride (HF), and water
• Hydrogen bonding - strong dipole-dipole interaction involving hydrogen
• Hydrogen bonding -

  • Water (H₂O)
  • Ethanol (C₂H₅OH)
  • Ammonia (NH₃)
  • Hydrogen fluoride (HF)
• Ion-dipole forces - between ions and polar molecules
• Ion-dipole forces -

  • NaCl
• Intermolecular forces are weaker than intramolecular forces
• Intermolecular - Determines physical properties.
• Intramolecular - Determines chemical properties
• Intermolecular - forces of attraction or repulsion which act between neighboring particles (atoms, molecules or ions)
• Intramolecular - forces that hold atoms together within a molecule.
• Properties affected by Intermolecular Forces -

  1. Surface Tension
  2. Viscosity
  3. Vapor Pressure
  4. Boiling point
  5. Molar Heat of vaporization
• Properties of Water -

  1. Polar molecule due to uneven distribution of electrons
  2. Exhibits hydrogen bonding
  3. High surface tension, adhesion, cohesion, and capillary action
• Melting Point - Solid to liquid
• Boiling point - liquid to Gas
• Heat of fusion - Energy needed to melt solid
• Heat of vaporization - Heat needed to vaporize liquid
• Crystalline - Regular arrangement, definite angles (e.g., diamond).
• Amorphous - No definite structure (e.g., glass)
• Ionic - Electrostatic attraction between ions (e.g., NaCl)
• Metallic - Shared valence electrons (e.g., copper).
• Covalent Network - Extended network of covalent bonds (e.g., diamond).
• Molecular - Held by intermolecular forces (e.g., H2O).
• Types of solids:

  1. Crystalline
  2. Amorphus
  3. Ionic
  4. Metallic
  5. Covalent Network
  6. Molecular