question_answer 81)

                                                                   Which of the following is not true about the 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

Answer:

                  (d) The fraction of octahedral or tetrahedral voids occupied depends upon the radii of the ions present at the lattice points. As we know 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.