Question

Atoms C and D form fcc crystalline structure. Atom C is present at the corners of the cube and D is at the face centres of the cube. What is the formula of the compound ?

Answer 1

Correct Answer - Formula of the compound =CD
Given : Crystal has fcc structure .
Atoms C are at 8 corners while atoms D are at 6 face centres of the cubic unit cell.
At the corner .`(1)/(8)` th of each C atom is present while at each face centre half of each D atom is present .
Number of the C atoms `= (1)/(8) xx 8 =1 `
Number of D atoms `= (1)/(2) xx 6 = 3`
Thus unit cell contains one C atom and three D atoms
Hence the formula of the compound is CD