In which pair most efficient packing is present?

Options

A. Hcp and bcc
B. hcp and ccp
C. bcc and ccp
D. bcc and simple cubic cell

Explanation

To determine which pair has the most efficient packing in solid-state chemistry, we need to compare the packing efficiencies of different types of unit cells. Here’s a step-by-step solution:

### Step 1: Understand Packing Efficiency
Packing efficiency is defined as the fraction of volume in a crystal structure that is occupied by the constituent particles (atoms, ions, or molecules). It is usually expressed as a percentage.

### Step 2: List the Common Types of Unit Cells and Their Packing Efficiencies
1. **Simple Cubic (SC)**:
- Packing Efficiency = 52%
2. **Body-Centered Cubic (BCC)**:
- Packing Efficiency = 68%
3. **Face-Centered Cubic (FCC)** or Cubic Close Packing (CCP):
- Packing Efficiency = 74%
4. **Hexagonal Close Packing (HCP)**:
- Packing Efficiency = 74%

### Step 3: Compare the Packing Efficiencies
From the above data, we can see:
- Simple Cubic has the lowest packing efficiency (52%).
- BCC has a moderate packing efficiency (68%).
- Both FCC and HCP have the highest packing efficiency (74%).

### Step 4: Identify the Most Efficient Packing Pair
Since both FCC and HCP have the same packing efficiency of 74%, they are the most efficient packing structures. Therefore, the pair that exhibits the most efficient packing is:
- **HCP and FCC (CCP)**

### Conclusion
The most efficient packing pair is **HCP and FCC (CCP)**.