Exam questions for CHEM203/253. Dr. Owen J. Curnow - DOC by 6sfasQ80


									                                              ENCH241 TEST
                                           Inorganic Chemistry
                                          Wednesday 7 May 2003

Time:         9:00 to 9:50 a.m.                                        Time allowed: 50 minutes
Answer ALL five questions. There are a total of 50 marks available.

1.      (15 marks)
        (a)      Sketch the radial distribution functions for the following orbitals:
                 (i)     1s
                 (ii)    3s
                 (iii)   4p

        (b)      Sketch the 2s and 4dxy orbitals illustrating both the radial and angular nodes.

2.      (10 marks)
        Three isomers having the formula N2CO are known: ONCN (nitrosyl cyanide), ONNC (nitrosyl
        isocyanide), and NOCN (isonitrosyl cyanide). Draw the most important resonance structure for
        each of these isomers and determine the formal charges. Which isomer do you predict to be the
        most stable (lowest energy) form?

3.      (10 marks)
        (a)      Draw and label the MO diagram for dinitrogen.

        (b)      What is the bond order of each of the following species and indicate which is/are
                 (i)     N2+
                 (ii)    N22–
4.   (7 marks)
     Consider the molecule


     (a)    What is the hybridisation on each non-hydrogen atom?

     (b)   Draw a picture showing the atomic and hybrid orbitals used in the above molecule for
           bonding and their overlap to form sigma and pi bonds. Put the valence electrons into the
           bonding orbitals.

5.   (8 marks)
     (a)    What factors govern the formation of molecular orbitals from atomic orbitals?

     (b)    What are triply-degenerate orbitals?

     (d)    What is the essential difference between a non-bonding and bonding orbital?

     (e)    Write the electron configuration for Mg in its ground state and for its first excited state.

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