Q31. Which of the following is not true about ionic solids?
(a) Bigger ions form the close packed structure.
(b) Smaller ions occupy either the tetrahedral or the octahedral voids depending upon their size.
(c) Occupation of all the voids is not necessary.
(d) The fraction of octahedral or tetrahedral voids occupied depends upon the radii of the ions occupying the voids.
The answer is (d) . This statement is not true about ionic solids since the radii of octahedral or tetrahedral void is related to radii of atoms (r) as
Radius of octahedral void (R0) = 0.414 r
Radius of tetrahedral void (R1) = 0.225r, where, r = radius of bigger atom involved.