When atom are placed at the corners of all 12 edges of a cube, how many atoms are present per unit cell?

Explanation

To determine how many atoms are present per unit cell when atoms are placed at the corners of all 12 edges of a cube, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure of the Cube**:
- A cube has 12 edges and 8 corners. Each edge connects two corners.

2. **Identify Atom Placement**:
- The problem states that atoms are placed at the corners of all 12 edges. However, each edge connects two corners, meaning that each corner atom is shared between adjacent edges.

3. **Count the Contribution of Corner Atoms**:
- Each corner atom is shared by 8 different unit cells (since a corner atom is part of 8 cubes that meet at that corner). Therefore, the contribution of each corner atom to the unit cell is \( \frac{1}{8} \).

4. **Count the Total Number of Corner Atoms**:
- There are 8 corners in a cube. Since each corner contributes \( \frac{1}{8} \) of an atom to the unit cell, the total contribution from all corners is:
\[ \text{Total contribution} = 8 \times \frac{1}{8} = 1 \text{ atom} \]

5. **Conclusion**:
- Therefore, the total number of atoms present per unit cell is **1 atom**.

### Final Answer:
The number of atoms present per unit cell is **1 atom**.