7a Calculate the radius ratios for LiF and LiI 7b Is this ra

7a. Calculate the radius ratios for LiF and LiI. 7b. Is this ratio consistent with LiF having a NaCl structure? Explain. 7c. What types of holes are Li+ ions likely to occupy in LiI? _____________________ 7d. In which ionic compound is the Li+ radius expected to be larger. Explain.

Solution

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

F-=147 , I-=100

r+/r-=74/147= 0.503 of LiF are the radius ratio

r+/r-=74/100=0.74 of LiI are radius ratio

ratio consistent with LiF having a NaCl structure is octahedral structure and LiF- Its structure is analogous to that of sodium chloride,