A cubic solid is made up of two elements X and Y . Atoms Y are present at the corners of the cube and atoms X at the body centre. What is the formula of the compound ?

Explanation

To determine the formula of the compound made up of elements X and Y, we need to analyze the arrangement of the atoms in the cubic solid.

### Step-by-Step Solution:

**Step 1: Identify the positions of the atoms.**
- The problem states that atoms of element Y are located at the corners of the cube, and atoms of element X are located at the body center of the cube.

**Step 2: Count the number of Y atoms.**
- In a cube, there are 8 corners. Each corner atom contributes \( \frac{1}{8} \) of an atom to the unit cell because it is shared by 8 adjacent unit cells.
- Therefore, the total contribution of Y atoms in one unit cell is:
\[ \text{Total Y atoms} = 8 \times \frac{1}{8} = 1 \]

**Step 3: Count the number of X atoms.**
- The body-centered atom (X) contributes fully to the unit cell since it is not shared with any other unit cell.
- Thus, the total contribution of X atoms in one unit cell is:
\[ \text{Total X atoms} = 1 \]

**Step 4: Write the formula based on the number of atoms.**
- From the calculations:
- Number of Y atoms = 1
- Number of X atoms = 1
- Therefore, the formula of the compound can be written as:
\[ XY \]

### Final Answer:
The formula of the compound is \( XY \).

---