The Structure for CaF₂ Can Be Described as a Face-Centered

question 28

Essay

The structure for CaF₂ can be described as a face-centered array of Ca²⁺ ions with F^- ions in the tetrahedral holes. The edge length of the unit cell is 5.45 × 10^-8 cm.A. What fraction of the tetrahedral holes must be occupied by F^- ions?
B. Calculate the density of CaF₂.C. If the ionic radius of F^- is 1.36 × 10^-8 cm, estimate the ionic radius of Ca²⁺. Tetrahedral holes are located along the body diagonals of each unit cell so that 1/4 (body diagonal) = r_Ca²⁺ + r_F^-.

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