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 ?

Explanation

To determine the formula of the compound made of elements X and Y, we can follow these steps:

### Step 1: Determine the number of atoms of X in the FCC structure.
In a face-centered cubic (FCC) arrangement, the number of atoms (Z) is calculated as follows:
- There are 8 corner atoms, each contributing 1/8 of an atom to the unit cell.
- There are 6 face-centered atoms, each contributing 1/2 of an atom to the unit cell.

Calculating the total:
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