6- shapes of molecules and intermolecular forces

• tetrahedral


  109.5
• pyramidal


  107
• non-linear


  104.5
• octahedral


  90
• linear


  180
• trigonal planar


  120
• most electronegative atoms

  nitrogen, oxygen, fluorine, chlorine
• electronegativity

  a measure of attraction of a bonded atom for the pair of electrons in a covalent bond
• non-polar

  with no charge separation across a bond or within a molecule
• permanent dipole

  a small charge difference that does not change across a bond, with s+ and s- partial changes on the bonded atoms
• permanent dipole-dipole interactions

  an attractive force between permanent dipoles in neighbouring polar molecules
• induced dipole-dipole interactions


  attractive forces between induced dipoles in different molecules
• hydrogen bond

  a strong dipole-dipole interaction between an electron-deficient hydrogen atom and a lone pair of electrons on a highly electronegative atom containing N, O or F on a different molecule
• polar substances dissolve in polar solvents


  non-polar substances dissolve in non-polar solvents
• dipole

  A separation in electrical charge so that one atom of a polar covalent bond, or one end of a polar molecule has a small positive charge s+ and the other has a small negative charge, s-
• polar (molecule)

  with s+ and s- charges at different ends of the molecule
• polar covalent bond

  a bond with a permanent dipole, having s+ and s- partial changes on the bonded atoms
• polar molecule

  a molecule with an overall dipole, having taken into account any dipoles across the bonds and the shape of the molecule
• Anomalous properties of water

  Ice is less dense than water

  Relatively high melting and boiling point