question_answer 76)

  In which of the following structures coordination number for cations and anions in the packed structure will be same?                           (a) Cl- ions form fee lattice and Na'1' ions occupy all octahedral voids of the unit cell (b) Ca2+ ions form fee lattice and F~ ions occupy all the eight tetrahedral voids of the unit cell (c) O2- ions form fee lattice and Na4' ions occupy all the eight tetrahedral voids of the unit cell (d) S2- ions form fee lattice and Zn21' ions go into alternate tetrahedral voids of the unit cell    

Answer:

                  (a) NaCI crystal have rock salt structure having fee lattice in which Cl~ ions are present at  fee lattice points and face Centre and Na+ occupies all the octahedral void of given unit cell.                                                                              Where, coordination number of Na+ = 6                                          coordination number of CI- = 6