A crystal is made of particles X, Y and Z.X forms fcc packing. Y occupies all the octahedral voids of X and Z occupies all the tetrahedral voids of X. If all the particles along one body diagonal are removed then the formula of the crystal would be:

No. of X particles per unit cell = 4 No. of Y particles = 4  No. of Z particles = 8 Along one body diagonal 2X atoms from 2 corners, one Y particle and 2Z particles will be removed. So, effective no. of X particles in a unit cell =4-18×2=154Effective no. of Y particles in a unit cell=4-1=3Effective no. of Z particles in a unit cell=8-2=6  X : Y : Z154 : 3 : 6 5 : 4 : 8