Question

How many zn 2+ ions are found on one body diagonal?

Answer 1

Explanation:

As the question says how many Zn²+ ions are found on one body diagonal of the FCC unit.
The answer to the above question is 4
Reason
In the ZnS type of cell, Zn²+ ions are located at the alternate voids of the tetrahedral structure
∴ 1 Zn²+ ion located at one body diagonal
i.e. no. of Zn²+ ions in     =  4*(no. of Zn²+ ion within the body) + 1
     FCC body diagonal
                                         =  4.

∴ There are 4 ions of Zn²+ present on the one body diagonal.

Answer 2

Answer:

Each body diagonal has one $Zn^{+2}$ ion only so that four body diagonals have four $Zn^{+2}$ ions

Explanation:

• In ZnS structure, $S^{-2}$ constitutes F.C.C
• Therefore, No of $S^{-2}$ = 8 × $\frac{1}{8}$ + 6 × $\frac{1}{2}$ = 4

• Therefore, No of Tetrahedral voids=8 and  $Zn^{+2}$  occupies half of the Tetrahedral voids alternatively.
• Therefore, each body diagonal has one $Zn^{+2}$ ion only