(A) and (B)

(C) and (D)

(A) and (C)

(B) and (D)

hcp and bcc

hcp and ccp

bcc and ccp

bcc and simple cubic cell

74

68

32

26

The coordination number is 12.

It has 74% packing efficiency.

Tetrahedral voids of the second layer are covered by the spheres of the third layer.

In this arrangement spheres of the fourth layer are exactly aligned with those of the first layer.

Cl (-) ion form fcc lattice and Na+ ions occupy all octahedral voids of the unit cell.

Ca2+ ions form fcc lattice and F? ions occupy all the eight tetrahedral

O2- ions form fcc lattice and Na+ ions occupy all the eight tetrahedral voids of the unit cell.

S2- ions form fcc lattice and Zn2+ ions go into alternate tetrahedral voids of the unit cell.