If three elements P, Q and R crystallise in a cubic unit cell with P atoms at the corners, Q atoms at the cubic centre and R atoms at the centre of each face of the cube, then write the formula of the compound.

Explanation

To determine the formula of the compound formed by the elements P, Q, and R in a cubic unit cell, we need to analyze the contribution of each type of atom based on their positions within the unit cell.

### Step-by-Step Solution:

1. **Identify the positions of the atoms:**
- P atoms are located at the corners of the cubic unit cell.
- Q atoms are located at the center of the cubic unit cell.
- R atoms are located at the center of each face of the cubic unit cell.
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