A solid is made of two elements X and Z. The atoms Z are in CCP arrangement while the atoms X occupy all the tetrahedral sites. What is the formula of the compound?

Tetrahedral sites are twice as compared to octahedral sites, then the ratio of X and Z is 2 : 1. Hence formula of the compound X2Z                                                                                                               ORZ-ccp arrangementZ  (Coordination number) for ccp  = 4 = Number of Z atomsNumber of tetrahedral holes = 2×ZC.N                                                            = 2×4 = 8Since X occupies  tetrahedral holes,therefore Number of atoms of X = 8 Z : X = 4 : 8            = 1 : 2 ⇒X2Z