• 1. Predict the lattice structures adopted by the following ionic solids ?
  • a-CaF₂
  • b- Li₂S
  • c-FeO₂
  • d-CrP

2. Zinc Blende is a structure commonly found for ionic solids of the type M2+X2-, but bonding in the eponymous ZnS has a significant amount of covalent character.

a. Calculate the ionic attraction between a Zn2+ cation and an S2- anion in the gas phase.

b. Using the Born-Landé equation, predict the lattice enthalpy for ZnS.

c. Draw a Born-Haber cycle for ZnS, and use it to determine the lattice enthalpy for ZnS .

d. Based on your answers to parts b and c, estimate the amounts of ionic and covalent bonding in ZnS.

3.Unlike C=O bonds, Si=O bonds are not thermodynamically stable, and rapidly convert to Si-O bonds.

a. Draw MO diagrams for CO2 and SiO2, considering both a possible linear (i.e. O=C=O and O=Si=O) and tetrahedral arrangement of the molecules.

b. Based on your MO diagrams from part a, propose a hypothesis as to why SiO2 forms repeating tetrahedral units, while CO2 forms discrete dimers.

c. What experiment could you conduct in order to test this hypothesis?