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					                                     CHEM 1315 -045
                                        Quiz #4

Name: KEY                                                              Date: 1 Nov 06

1. Write the Lewis structures for the following: (3 points)
   (a) SiH4 8e-, 4 pairs                     (b) H2O2 14e-, 7 pairs

   (c) C2F6 (contains a C-C bond) 50e-, 25 pairs (d) AsO3-3 26e-, 13 pairs

   (e) H2SO3 (H is bonded to O) 26 e-, 13 pairs (f) C2H2 10e-, 5 pairs

2. (a) Determine the formal charge on the chlorine atom in the hypochlorite ion, ClO-,
   and the perchlorate ion, ClO4-, if the Cl atom has a full octet: (3 points)
  perchlorate has 14e-, 7 pairs                                chlorate has 32 e-, 16 pairs

  (b) What are the oxidative numbers of the chlorine in ClO- and in ClO4-?
       Perchlorate is +1, Chlorate is +7 (ClO4)

  (c) What are the essential differences in the definitions of formal charge and oxidation
   number that lead to the differences in the answers to parts (a) and (b)?

        Formal charge assumes bonds equally share electron (e-) pair (all bonds are
purely covalent.) Oxidative number assumes more electronegative element higher
position that formal charge. Formal charge = bonded e- - unbounded e- (? FC)

3. Draw the Lewis structure for each of the following molecules or ions and predict
   their electron-domain and molecular geometries. (4 points)
  (a) PF3 26 e-, trigonal pyramidal          (b) CH3+ 6e-, trigonal planar

 (c) BrF3 28e-, T-shaped                       (d) ClO4- 32 e-, tetrahedral

 (e) XeF2 linear, 22 e-                        (f) BrO2- bent, 20 e-

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