Question

What is the coordination number of NaCL , CsCL, ZnS and CaF2?

Answer 1

 1.NaCl  Anion forms fcc unit  cell,  cation occupies half of tetrahedral voids,  CN is 6 for both.
2.  CsCl: Anion forms bcc unit cell,  cation occupies body center, CN is 8 for both
3. ZnS :   Anion forms fcc unit  cell, cation occupies alternate tetrahedral voids, CN is 4 for both
4. CaF2: Anion forms bcc unit cell, cation occupies alternate body center, CN is 4 for anion and 8 for cation.