Chp 6

• 2 bonding pairs, 0 lone pairs

  Angle - 180

  Name - linear
• 3 bonding pairs ,0 lone pairs

  Angle - 120 Name - trigonal planar
• 2 bonding pairs, 1 lone pair 


  Angle - 118 Name - bent
• 4 bonding pairs, 0 lone pairs

  Angle - 109.5

  Name - tetrahedral
• 3 bonding pairs, 1 lone pairs

  Angle - 107

  Name - trigonal pyramidal
• 2 bonding pairs, 2 lone pairs 


  Angle - 104.5

  Name - Bent
• 5 bonding pairs, 0 lone pairs

  Angle - 90 and 120

  Name - Trigonal bipyramidal
• 6 bonding pairs, 0 lone pairs

  Angle - 90

  Name - octahedral
• 4 bonding pairs, 2 lone pairs

  Angle - 90

  Name - Square planar
• Define electronegativity


  The ability of an atom of an element to attract the bonding electrons in a covalent bond
• What is a polar covalent bond?


  When the shared electrons in a covalent bond are drawn to the atom with a greater electronegativity resulting in partial positive and negative charges
• What is a polar bond?

  A bond with a permanent dipole due to a difference in electronegativity between atoms
• What is a polar molecule?


  Molecules which contains 1 or more polar bonds, which don't cancel out due to unbalanced dipoles or the shape of the molecule
• What are intermolecular forces?


  Weak attractive forces that act between molecules.

  They occur between all atoms and molecules
• How do London forces arise?

  1 - electrons constantly move rapidly

  2 - at any moment in time there may be an uneven distribution of electrons

  3 - this causes an instantaneous dipoles to arise

  4 - the instantaneous dipole can cause an induced dipole to arise in neighbouring atoms

  5 - this results in an attractive force
• What are the factors affecting strength of London forces?

  The no of electrons in a atom of a molecule

  Points of contact between molecules
• What is the difference in boiling point in straight chain and branched molecules?

  Straight chain molecules have greater points of contact between adjacent molecules

  Therefore there are greater London forces present in adjacent molecules than branched molecules

  Therefore straight chain molecules have a higher mp and bp
• How do permanent dipoles arise?

  Arise due to electronegativity difference between atoms

  Partial negative end of a polar molecule can be attracted to a partial end of of another molecule

  This causes a pd-pd attraction to arise between polar molecules
• When can h bonding occur?

  When H is covalently bonded to F, N or O
• Properties of ice


  Floats as ice is less dense than water

  Ice expands when water freezes

  Hydrogen bonds hold water molecules apart in an open lattice structure

  Water molecules in ice are further apart than in water

  Has higher BP than expected