In the primitive cubic unit cell, the atoms are present at the:

Options

A. corners of the unit cell
B. centre of the unit cell
C. centre of each face of the unit cell
D. one set of faces of the unit cell

Answer

To solve the question regarding the positions of atoms in a primitive cubic unit cell, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure of a Primitive Cubic Unit Cell**:
- A primitive cubic unit cell is one of the simplest types of unit cells in crystallography. It is defined by having atoms located at its corners.

2. **Identify the Positions of Atoms**:
- In a primitive cubic unit cell, there are a total of 8 corners. Each corner of the cube has one atom located at it.

3. **Count the Atoms**:
- Since there are 8 corners in the unit cell, and each corner contributes 1/8 of an atom to the unit cell (because each corner atom is shared among 8 adjacent unit cells), the total number of atoms effectively present in the unit cell is:
\[ \text{Total atoms} = 8 \times \frac{1}{8} = 1 \text{ atom} \]

4. **Conclusion**:
- Therefore, in the primitive cubic unit cell, the atoms are present at the corners of the unit cell.

5. **Select the Correct Option**:
- Based on the analysis, the correct answer to the question is that the atoms are present at the corners of the unit cell.

### Final Answer:
The atoms in a primitive cubic unit cell are present at the **corners of the unit cell**.

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