1. For each pair, circle the most polar bond
   1. C—F                 O—F                

• O—Cl               S—Br               

• C—S                 B—F                

• C—P                 N—F

• N—O                C—O

•   By referring only to the periodic table, select most electronegative element in each pair
  • Al         or         Si
  • F          or         N
  • Ga        or         P
  • Na        or         K
  • Br         or         Pb
• Write Lewis structures that obey the octet rule for each of the following, and assign formal charges to each atom
  • CF₄

• BrO₃^–

• Write Lewis structures for the following

H₂CO (both H atoms are bonded to C)                                                    NF₃

AsO₃^3-                                                                           C₂H₂

O₃                                                                                 NO

BF₃                                                                               XeF₄

• Write the Lewis Structures for the following molecules.  Based on Lewis structures, predict which molecule will have the longest N—O bond lengths: NO⁺, NO₂^–, and NO₃^–.

• OCS, has three possible Lewis structures. (a) Draw these three structures and assign formal charges in each. (b) Which Lewis structure is dominant?  Treat C as the central atom in each of the three Lewis structures

O      C      S                   O     C     S                     O     C     S

• Using Table 8.4, estimate DH for the following reactions and indicate whether they are exothermic or endothermic