2B - Review

        1.   This question is about different models of bonding and molecular shapes.  Magnesium sulfide shows ionic bonding.

                 (i)      What is meant by the term ionic bonding?  [1]

                (ii)      Draw a ‘dot-and-cross’ diagram to show the bonding in magnesium sulfide. Show outer electron shells only.  [2] 

        2.       ‘Dot-and-cross’ diagrams can be used to predict the shape of covalent molecules.

              Fluorine has a covalent oxide called difluorine oxide, F₂O. The oxygen atom is covalently bonded to each fluorine atom.

                 (i)      Draw a ‘dot-and-cross’ diagram of a molecule of F₂O.  Show outer electron shells only.  [2]

                 (ii)      Predict the bond angle in an F₂O molecule. Explain your answer.  [3] 

        3.       Chemists have developed models for bonding and structure which are used to explain different properties.

                  Ammonia, NH₃, is a covalent compound.

                  (i)      Explain what is meant by a covalent bond.  [1]

                 (ii)      Draw a ‘dot-and-cross’ diagram to show the bonding in NH₃.  Show outer electrons only.  [1]

                (iii)     Name the shape of the ammonia molecule and explain, why ammonia has this shape and has a bond angle of 107°.  [3] 

        4.       Molecules of NCl₃ have a bond angle of 107°.

                  (i)      Name the shape of an NCl₃ molecule.  [1] 

                 (ii)      Explain why a molecule of NCl₃ has this shape and a bond angle of 107°.  [3] 

        5.       Antimony is in Group 5 of the Periodic Table. It forms a compound with hydrogen that has the formula SbH₃.

                 (i)      Predict the bond angle in SbH₃.  [1]

                (ii)      Explain why a molecule of SbH₃ has this bond angle.  [2]

        6.       The ‘dot-and-cross’ diagram of an ammonia molecule is shown below.

                Predict, with reasons, the bond angle in an ammonia molecule.  [4]