Discussion:
Simple Solids - Structures
1. Draw one layer of close-packed spheres. On this layer mark the positions of the centers of the B layer atoms using the symbol X and, with the symbol O mark the positions of the centers of the C layer atoms of an fcc lattice.
2. Consider the structure of rock salt. (a) What are the coordination numbers of the anion and cation? (b) How many Na+ ionsoccupy second-nearest neighbor locations of an Na+ ion? (c) Pick out the closest-packed plane of CI- ions. (Hint: this hexagonal plane will be perpendicular to a threefold axis).
3. Consider the structure of cesium chloride. (a) What is the coordination number of the anion and cation? (b) How many Cs+ ions occupy second-nearest neighbor locations of a Cs+ ion?
4. (a) How many Cs+ ions and how many CI- ions are in the CsCI unit cell? (b) How many Zn2+ ions and how many S2- ions are in the sphalerite unit cell?
5. Given the following data for the length of a side of the unit cell for compounds "that crystallize in the rock-salt structure, determine the cation radii: MgSe (5.45 A). CaSe (5.91A). SrSe (6.23 A), BaSe (6.62 A.). (To determine the Se2- radius, assume that the Se2- ions are in contact in MgSe).