The number of atoms in a unit cell of a cubic crystal system is 2, the arrangement of atoms is

Options

A. body centred cubic
B. face centred cubic
C. end centred cubic
D. simple cubic

Explanation

To determine the arrangement of atoms in a cubic crystal system with 2 atoms per unit cell, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Unit Cell**:
- A unit cell is the smallest repeating unit in a crystal lattice. In a cubic crystal system, the unit cell can be of different types: Simple Cubic (SC), Body-Centered Cubic (BCC), and Face-Centered Cubic (FCC).

2. **Identifying the Number of Atoms**:
- The question states that there are 2 atoms in the unit cell. We need to identify which type of cubic arrangement corresponds to this number.

3. **Analyzing the Types of Cubic Structures**:
- **Simple Cubic (SC)**: Contains 1 atom per unit cell (1 atom at each corner contributes 1/8 of an atom from each of the 8 corners: 8 * 1/8 = 1).
- **Body-Centered Cubic (BCC)**: Contains 2 atoms per unit cell (1 atom at each of the 8 corners contributes 1/8 from each corner: 8 * 1/8 = 1, plus 1 atom at the body center).
- **Face-Centered Cubic (FCC)**: Contains 4 atoms per unit cell (1 atom at each of the 8 corners contributes 1/8 from each corner: 8 * 1/8 = 1, plus 1 atom at each of the 6 faces contributing 1/2 from each face: 6 * 1/2 = 3, totaling 4).

4. **Conclusion**:
- Since we have established that the BCC structure has 2 atoms per unit cell (1 from the corners and 1 from the body center), we conclude that the arrangement of atoms in this case is Body-Centered Cubic (BCC).

### Final Answer:
The arrangement of atoms in a cubic crystal system with 2 atoms per unit cell is **Body-Centered Cubic (BCC)**.