For a cell of the CsCl type (figure 9.18), how is the length of one side of the cell,s, related to the sum of the radii of the ions, r subscript cation + r subscript anion?

Question

Figure 9.18 :
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Another question : Consider the NaCl unit shell in figure 9.18. looking at only the front face, five large cl- ions, 4 small na+ ions, how many cubes share each of the na+ ions in this face? how many cubes share each of the Cl- ions in this face?