Ch. 12 chemical bonds                        test                               65  points                                             chemistry

Problems / questions are based on your homework assignment.

1. Write the Lewis structure for each of the following simple molecules.  Show all bonding valence electron pairs as lines and all nonbonding valence electron pairs as dots.  For those molecules that exhibit resonance, draw the various possible resonance forms.  [15 points]

a. Dichlorine monoxide (central atom is oxygen)

b. Cl4

c. Sulfur trioxide

2. Chemical bonds  [6 points]

a. What type of bonding requires the complete transfer of an electron from one atom to another ?

b. What type of bonding involves the sharing of (either equally or unequally) of electrons between atoms ?

c. Describe the type of chemical bonding that exists between the atoms in the hydrogen molecule, H2 ?

3. For each of the following sets of elements, identify the element expected to the most electronegative and that expected to be least electronegative ?  [4 points]

a.  K, Sc, Ca

b. C, O, N

4. What general principles determine the molecular structure (shape) of a molecule ?  [5 points]

5. Although both BF3 and NF3 molecules contain the same number of atoms, the BF3 molecule is flat, whereas the NF3 molecule is not flat.  Explain.  [10 points]

6.Sketch the shape of the molecule, it’s bond angle(s), and the name of the shape of the molecule.  [10 points]

a. GeI4

b. SF4

7. Will the following molecules be polar or nonpolar; justify / rationalize your answer.  [15 points]

a. SF4  [hint:  see 6b]

b. NF3  [hint:  see 5]

c. PF5

8. Briefly, describe valence bond theory; include / describe “overlap” in your answer. [10 points extra credit]