Question

Answer question 23-25

The unit cell for HCP is not a cube. This structure is made by placing one flat layer of a close packed hexagon arrangement of seven spheres on top of the holes in another layer, a third layer directly above first layer, and so on. This layering is referred to as A,B,A,B. Hold the model up to the light and note the tunnels that pass straight through the structure. See the figure below. 23. What is the coordination number of every sphere? Part 2: Packing Arrangements for lons As with neutral atoms in Part 1, we will regard monatomic ions as perfect spheres. 24. Generally, in terms of electronic configurations, why are anions larger than cations? 25. Give a pair of ions, one cation and one anion, which do not follow the generalization in number twenty-four above.