In a face centred cubic cell, an atom at the face centre is shared by-

Options

A. 4 unit cells
B. 2 unit cells
C. 1 unit cell
D. 6 unit cells

Answer

To solve the question regarding how many unit cells share an atom located at the face center of a face-centered cubic (FCC) cell, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the FCC Structure**:
- A face-centered cubic (FCC) unit cell has atoms located at each of the corners of the cube and one atom at the center of each face.

2. **Identifying the Faces**:
- There are a total of 6 faces in a cube. Each face has one atom located at its center.

3. **Sharing of Atoms**:
- An atom located at the center of a face is shared between two adjacent unit cells. This is because the face-centered atom is positioned such that half of it belongs to one unit cell and the other half belongs to the adjacent unit cell.

4. **Conclusion**:
- Therefore, the atom at the face center of a face-centered cubic cell is shared by **2 unit cells**.

### Final Answer:
The atom at the face center of a face-centered cubic cell is shared by **2 unit cells**.

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