Question

An ionic compound is formed by two elements A and B.The atoms of element B form fcc structure and the atoms of A occupy 1/3rd of tetrahedral voids. What is the
formula of the ionic compound?

Answer 1

Answer:

A4B8 or AB2

Explanation:

Atom 'A' at FCC lattice points means number of atom A in unit cell is:

8

1

×8+

2

1

×6=4.

If in a close-packed structure (ccp or fcc) there are 'n' atoms or ions then the number of tetrahedral voids will be 2n. Thus the number of atom B is =2×4=8

Thus the compound is A

4

B

8

or AB

2