inter molecular forces

• what are inter-molecular forces?


  the electrostatic attraction between oppositely charged ends of neighbouring molecules. they are weak forces.
• whats a macromolecule?


  no intermolecular forces
• what is electronegativity?


  the power of an atom to attract an electron pair from within a covalent bond.
• what are the two reasons partical charges occur in molecules?

  -elecronegativity difference between bonded atoms

  -asymmetry of electron clouds
• what are two poles called?

  dipoles
• what three things does the electronegativity of an atom depend on?


  atomic radius

  shielding

  proton number
• how does atomic radius change the electronegativity of an atom?


  the smaller the atomic radius means the nucleus is closer to the bonding pairs causing a stronger pull and higher electronegativity
• how does the proton number of an atom change its electronegativity?


  the greater the proton number, greater the electronegativity because there is a stronger pull from nucleus an bonding electrons( assuming similar radius)
• how does shielding effect the electronegativity on an atom?


  increased shielding, lower electronegativity because there is a weaker attraction between nucleus and bonding pairs.
• why do group 8 elements not have electronegativity?


  the dont naturally form covalent bonds
• what are the 3 main types of intermolecular forces?

  • van der waals forces
  • permanent dipole
  • hydrogen bonding
• what are van der waal forces?

  • weakest type of intermolecular forces
  • acts as an induced dipole between molecules
• whats hydrogen bonding?

  • strongest type of intermolecular forces
  • only forms between hydrogen and nitrogen, oxygen and fluorine with a hydrogen atom from another molecule
  • have a high melting and boiling point
• what are permanent dipole intermolecular forces?

  • acts between molecules with a polar bond
  • regions attract each other hold the molecules together in a lalttice like structure
• what is the origin of van der waal forces?

  • random asymmetry of electron cloud forms a temporary dipole
  • temporary dipole induces a dipole on neighbouring molecule
  • temporary dipole attracts induced dipole