The correct order of the packing efficiency in different types of unit cells is______________

Options

A. fcc lt bcc lt simple cubic
B. fcc gt bcc gt simple cubic
C. fcc lt bcc gt simple cubic
D. bcc ltfcc = simple cubic

Explanation

To determine the correct order of packing efficiency in different types of unit cells, we need to understand the concept of packing efficiency and the packing efficiencies of the various unit cells.

### Step-by-Step Solution:

1. **Understanding Packing Efficiency**:
- Packing efficiency (PE) is defined as the percentage of the total volume of a unit cell that is occupied by the constituent particles (atoms, ions, or molecules).
- It is calculated using the formula:
\[ \text{Packing Efficiency (PE)} = \left( \frac{\text{Volume occupied by particles}}{\text{Total volume of unit cell}} \right) \times 100 \]

2. **Identifying Types of Unit Cells**:
- The three types of unit cells we will consider are:
- Simple Cubic (SCC)
- Body-Centered Cubic (BCC)
- Face-Centered Cubic (FCC)

3. **Finding Packing Efficiency Values**:
- **Simple Cubic (SCC)**:
- Packing Efficiency = 52%
- **Body-Centered Cubic (BCC)**:
- Packing Efficiency = 68%
- **Face-Centered Cubic (FCC)**:
- Packing Efficiency = 74%

4. **Arranging the Packing Efficiencies**:
- Now, we can arrange the packing efficiencies in descending order:
- FCC (74%) > BCC (68%) > SCC (52%)

5. **Conclusion**:
- The correct order of packing efficiency in different types of unit cells is:
\[ \text{FCC} > \text{BCC} > \text{SCC} \]

### Final Answer:
The correct order of the packing efficiency in different types of unit cells is **FCC > BCC > SCC**.