A unit cell consists of a cube in which X atoms at the corners and Y atoms are at the face centres. If two atoms are missing from two corners of the unit cell , what is the formula of the compound ?

Explanation

To find the formula of the compound based on the given information about the unit cell, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Contribution of Atoms**:
- In a cubic unit cell, there are 8 corners and 6 face centers.
- Each corner atom contributes \( \frac{1}{8} \) of an atom to the unit cell because it is shared among 8 unit cells.
- Each face-centered atom contributes \( \frac{1}{2} \) of an atom to the unit cell because it is shared between 2 unit cells.
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