Potassium bromide, KBr, crystallizes like NaCl in a face-centered lattice. The ionic radii of K⁺ and Br^- ions are 133 pm and 195 pm, respectively. Assuming that all Br^- ions are positioned in the face and corners of the unit cell, while the K⁺ ions are positioned along the edge alternating between anions, calculate the length of a unit cell edge. A) 230 pm B) 328 pm C) 523 pm D) 656 pm E) 780 pm

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Quizplus · Accepted Answer

In a face-centered cubic lattice like NaCl, the edge length (a) can be calculated using the formula: a = 2 * (r_K+ + r_Br-), where r_K+ and r_Br- are the ionic radii of K+ and Br- respectively. Substituting the given values, a = 2 * (133 pm + 195 pm) = 656 pm.

Potassium Bromide, KBr, Crystallizes Like NaCl in a Face-Centered Lattice