Name:

1. Predict whether the following compounds are ionic or covalent: KI, MgS, CS₂, P₄O₁₀, AL₂O₃, I₂
   

2. In which of the following does the central atom obey the octet rule?: NO₂, SF₄, NH₃, SO₃, O₂^- SF₆.
    Are any of them odd-electron molecules? Identify.
   

3. Define bond dissociation energy.

4. What is the principle of electroneutrality? Use this rule to exclude a possible resonant structure of CO₂
   

5. What is the difference between the electron pair geometry and the molecular geometry of a molecule?
    Use the water molecule as an example in your discussion.
   

6. Which compound has the most negative energy of ion pair formation (lattice energy)?: NaCl, MgS, MgF₂.
   

7.Place the following compounds in order of increasing lattice energy: LiI, LiF, CaO, RbI.
   

8. Draw Lewis structures for the following molecules and ions: NF₃, HOBr, ClO₃^-, SO₃^-, BrF₃, I₃^-, XeF₃⁺.
   

9. Show all of the possible resonant structures for each the following molecules or ions: SO₂, NO₂^-, SCN^-
   

10. Determine the formal charges on each element in the following molecules and ions: N₂H₄, PO₄^-3, BH₄^-, NH₂OH:
    

11. For each pair of bonds, indicate the more polar bond and use an arrow to show the direction of polarity in
     each bond.
     C -- O   and  C -- N
     P -- Br  and   P -- Cl
     B -- O   and  B -- S
     B -- F    and  B -- I
   

12. Two resonant structures are possible for NO₂^-. Draw them and then determine the formal charge on each
      atom in each resonant structure. If a H⁺ ion is attached to HNO₂^-, does it attach to the O or to the N?
     

13. Consider the carbon--oxygen bond in formaldehyde (CH₂O) and carbon monoxide (CO). In which molecule
     is the C--O bond shorter? In which molecule is it stronger?
    

14. Draw the Lewis structure for each of the following molecules and ions. Describe the electron pair geometry and
     the molecular geometry:
      NH₂Cl, Cl₂O (O is central), SCN^-, HOF
    

15. Consider the following molecules: H₂O, NH₃, CO₂, ClF, CCl₄.
      In which compound are the bonds most polar?
      Which compounds in the list are nonpolar?

16. Examine the trends in lattice energy in table 9.3. The value of the lattice energy becomes somewhat more negative
     on going from NaI to NaBr to NaCl, and all are in the range of -700 to -800 kJ/mol. Suggest a reason for the
     observation that the lattice energy of NaF is much more negative than the other sodium halides.
     

17. Using the bond energies in table 9.9 on page 356, calculate the heat of combustion of gaseous methane (CH₄)
     when it combines with oxygen to produce carbon dioxide and water.