In the ionic compounds LiF, NaCl, KBr, and RbI, the measured cation-anion distances are 2.01 Ã… (Li-F), 2.82 Ã… (Na-Cl), 3.30 Ã… (K-Br), and 3.67 Ã… (Rb-I), respectively.
(a) Predict the cation-anion distance using the values of ionic radii given in Figure 7.7. (b) Calculate the difference between the experimentally measured ion-ion distances and the ones predicted from Figure 7.7. Assuming we have an accuracy of 0.04 Ã… in the measurement, would you say that the two sets of ion-ion distances are the same or not? (c) What estimates of the cation-anion distance would you obtain for these four compounds using bonding atomic radii? Are these estimates as accurate as the estimates using ionic radii?

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Group 1A Group 2A Group 3A roup 6A Group 7A Be2+ 0.59 B3+ 0.41 0.90 1-34 0.90 0.82 0.73 0.71 A13+ 0.68 Cl 1.67 0.86 Mg 1.30 CI 0.99 18 Ca2+ 1.14 Ga3+ 0.76 152 1.82 1.96 1.24 1.26 116 Te 1.66 0,94 2.06 Rb 2.11 In 144 192 - cation - anionn neutral atom