Calculate the ratio of the alkali metal bromides on the basis of the data given below and predict the form of the crystal structure in each case. Ionic radii (in pm) are given below Li+ = 74, Na+ = 102, K+ = 138 Rb+ = 148, Cs+ = 170, Br- = 195
Answer -
The ratio of cation to that of anion i.e. r+/r– gives the clue for crystal structure Li+ / Br– 74 / 195 = 0.379 Tetrahedral
Na+ / Br– 102 / 195 = 0.523 Octahedral
K+ / Br– 138 / 195 = 0.708 Octahedral
Rb+ / Br– 148 / 195 = 0.759 Body centered
Cs+ / Br– 170 / 195 = 0.872 Body centered
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