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?

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