2C - Bonding and structure review  /39

     1)    Arrange the elements of Group 7 in order of increasing boiling points.  Explain your answer.  [4]

                 Down the group  [1]  As you go down the Group, the molecules have more electrons [1]

            which gives a greater uneven distribution of electrons [1] 

            giving stronger instantaneous dipole - induced dipole forces of attraction [1]

 

     2)    Describe how Van der Waals' forces arise. [6]

                 Electrons in shells are continually moving [1]   the electrons are continually fluctuating [1]

            this creates an uneven distribution of electrons [1]  which sets up an instantaneous dipole [1]

            this induces a dipole in neighbouring atoms / molecules [1]  creating weak forces of attraction [1]

 

     3)    State whether the following molecules are polar or non polar:  [7]

            a)  Define electronegativity [1] 

                 The power of an atom in a molecule to attract bonding pair electrons towards itself [1]

 

  b)  H2S c)  CH4 d)  CH3OH e)  I2 f)  CH3NH2 g)  PH3
  Polar Non polar Polar Non polar Polar Polar

 

     4)    State the type of intermolecular forces that exist between the following molecules:  [6]

 

  a)  H2S b)  CH4 c)  CH3OH d)  I2 e)  CH3NH2 f)  PH3
  PD - PD VDW H - B VDW H - B PD - PD

         5)    Draw intermolecular force between 2 molecules of water.  Include any dipoles [2]:

            Labelled bond between LP and H [1] Dipoles shown [1]

                                                                                                       

 

 

     6)    Describe metallic bonding and use your diagram to explain whether it conducts electricity.

            You may wish to use a diagram. [3]

                                

            Labelled diagram [1]  electrostatic forces of attraction between delocalised electrons and metal ions [1]

            The electrons are free to move [1]

 

     7)    Discuss the conductivity of ionic compounds compared with simple covalent structures.  Explain your answer.  [6]

                 Ionic:  Solids do not conduct [1]  as the ions are held in a fixed position [1]

            Dissolved [1] and molten [1] as the ions are free to move [1]

            Covalent:  Does not conduct electricity as there are no free moving charges [1]

 

     8)    With the aid of diagrams discuss and explain the solubility of sodium chloride and Iodine in water.  [5]

                 Ionic diagram of both ions surrounded by water molecules [1]  Water is a polar molecule [1] 

            These are attracted to the ions, weaken the ionic bonds pulling them away from the lattice [1]

            Iodine is a non polar molecule [1] which is too weak to break the hydrogen bonds in water [1]