A solid is made of two elements X and Y. Atoms X are in fcc arrangement and Y atoms occupy all the octahedral sites and alternate tetrahedral sites. What is the formula of compound ?

Answer

`XY_2`

Explanation

For each X atom, there are one octahedral and two tetrahedral sites.
No. of Y atoms in octahedral sites = 1 per X atom
Since alternative (i.e., half) tetrahedral sites are occupied ,
No. of Y atoms in tetrahedral sites = 1 per X atom
Total Y atoms = 2 per X atom
`:. ` Formula = `XY_2`