1. Consider the Following Ionization Energies for Aluminum

Atomic Structure and Bonding Problem Set Due April 4, 2015

1. Consider the following ionization energies for aluminum: + Al(g)  Al (g) + e- I1 = 580 kj/mol + 2+ Al (g)  Al (g) + e- I2 = 1815 kj/mol +2 3+ Al (g)  Al (g) + e- I3 = 2740 kj/mol +3 4+ Al (g)  Al (g) + e- I3 = 11,600 kj/mol Explain completely the trend in ionization energies shown above.

2. Explain the following a. The electron affinity for sulfur is more exothermic than that for oxygen. How do you account for this? b. Atomic radii decreases from Na to Cl in the periodic table. c. Each element displays a unique gas-phase emission spectrum.. d. Iron is paramagnetic e. Nitrogen is more electronegative than boron but less electronegative than fluorine

3. Using graph paper draw the expected PES spectra for silicon and for iron using two separate graphs.

4. Explain completely what part of the Bohr theory of the atom is considered unsatisfactory as a result of the Heisenberg uncertainty principal.

5. The lattice energies of FeCl3, FeCl2 and Fe2O3 are (in no particular order) -2631, -5359, and -14,774 kj/mol. Match the appropriate formula to each lattice energy. Explain completely.

6. Identify the five compounds of H, N and O described as follows. For each compound, write a Lewis structure that is consistent with the information given. a. All the compounds are electrolytes, although not all of them are strong electrolytes. Compound C and D are ionic and compound B is covalent b. Nitrogen occurs in its highest possible-oxidation state in compounds A and C; nitrogen occurs in its lowest possible oxidation state in compounds C, D and E. The formal charge on both nitrogens in compound C is +1; the formal charge on the only nitrogen in compound B is 0. c. Compound A and E exist in solution. Both solutions give off gases. Commercially available concentrated solutions of compound A are normally 16 M. The commercial concentrated solution of E is 15 M. d. Commercial solutions of compound E are labeled with a misnomer that implies that a binary gaseous compound of nitrogen and hydrogen has reacted with water to produce ammonium ions and hydroxide ions. Actually, this reaction occurs to only a slight extent. e. Compound D is 43.7 % N and 50.0 % O by mass. If compound D were a gas at STP, it would have a density of 2.86 g/L. f. A formula unit of compound C has one more oxygen than a formula unit of compound D. compound C and A have one ion in common when compound A is acting as a strong electrolyte. g. Solutions of compound C are weakly acidic; solutions of compound A are strongly acidic; solutions of compounds B and E are basic. The titration of 0.726 g compound B requires 21.98 ml of 1.000 M HCl to complete neutralization.

7. The skeletal structure of N, N-dimethylformamide molecule is

H-C(O)-N(CH3)2

a. Draw the Lewis Diagram b. Various types of evidence lead to the conclusion that there is some double bond character to the C-N bond. Draw one or more resonance structures that support this observation. c. Choose the Lewis structure that will predominate d. Identify the hybridization on each atom e. Identify all sigma and pi bonds.

8. An unusual category of acids known as super acids, which are defined as any acid stronger than 100% sulfuric acid, can be prepared by seemingly simple reactions similar to the one below. In this example, the reaction of + - anhydrous HF with SBF5 produces the super acid [H2F] [SbF6] : a. What are the molecular structures of all species in this reaction? b. What are the hybridizations of the central atoms in each species? + - c. What mass of [H2F] [SbF6] can be prepared when 2.93 ml anhydrous

HF (density = 0.975 g/ml) and 10.0 ml SbF5 (density = 3.10 g/ml) are allowed to react?

9. Determine the molecular structure and hybridization of the central atom X in + the polyatomic ion XY3 given the following information; A neutral atom of X contains 36 electrons, and the element Y makes an anion with a 1- charge, which has the electron configuration 1s22s22p6.

10. Which of the following statements about intermolecular forces is (are) true? If false explain why? a. London dispersion forces are the only type of intermolecular forces that nonpolar molecules exhibit. b. Molecules that have only London dispersion forces will always be gases at room temperature. c. The hydrogen-bonding forces in HN3 are stronger than those in H2O.

d. The molecules in SO2(g) exhibit dipole-dipole intermolecular interactions. e. CH3CH2CH3 has stronger London dispersion forces than does CH4

f. CCl4 dissolves in hexane due to dipole-dipole forces.

11. In each of the following groups of substances, pick the one that has the given property. Justify your answer.

a. highest boiling point: HBr, Kr or Cl2 b. highest freezing point: H2O, NaCl or HF o c. lowest vapor pressure at 25 C: Cl2, Br2 or I2. d. lowest freezing point: N2, CO, or CO2

e. lowest boiling point: CH3, CH3CH3, or CH3 CH2CH3 f. highest boiling point: HF, HCl or HBr

g. Most soluble in water: HBr, Kr or Cl2 g. most soluble in hexane: HF, HCl or HBr

12. Consider the following melting point data:

Compoun NaCl MgCl2 AlCl3 SiCl4 PCl3 SCl2 Cl2 d Mp (oC) 801 708 190 -70 -91 -78 -101

Compoun NaF MgF2 AlF3 SiF4 PF5 SF6 F2 d Mp(oC) 997 1396 1040 -90 -94 -56 -220 Account for the trends in melting points.