Which statements is/are correct ?

Options

A. The packing factor for HCP and CCP are same
B. The co-ordination number for HCP and CCP is same
C. The number of particles for both unit cell are same
D. The void fraction for FCC is greater than HCP

Answer

To determine which statements are correct regarding the structures of Simple Cubic Packing (SCP) and Cubic Close Packing (CCP), we will analyze each statement step by step.

### Step 1: Understanding Packing Factor
The packing factor is defined as the fraction of volume in a crystal structure that is occupied by the constituent particles (atoms, ions, or molecules).

- **For SCP (Simple Cubic Packing)**: The packing factor is 74%.
- **For CCP (Cubic Close Packing)**: The packing factor is also 74%.

**Conclusion**: The packing factors for SCP and CCP are the same.

### Step 2: Coordination Number
The coordination number is the number of nearest neighbors surrounding a particle in a crystal structure.

- **For SCP**: The coordination number is 12.
- **For CCP**: The coordination number is also 12.

**Conclusion**: The coordination numbers for SCP and CCP are the same.

### Step 3: Number of Particles in Unit Cells
The number of particles in a unit cell differs between SCP and CCP.

- **For SCP**: There is 1 particle per unit cell.
- **For CCP**: There are 4 particles per unit cell.

**Conclusion**: The number of particles in the unit cells of SCP and CCP is not the same.

### Step 4: Comparing FCC and SCP
FCC (Face-Centered Cubic) is another name for Cubic Close Packing (CCP).

- The statement that FCC is greater than SCP is incorrect because they are equivalent in terms of packing efficiency and coordination number.

**Conclusion**: FCC and SCP are equal in terms of packing efficiency and coordination number.

### Final Summary
- **Statement A**: Correct (Packing factor of SCP and CCP is the same, 74%).
- **Statement B**: Correct (Coordination number of SCP and CCP is 12).
- **Statement C**: Incorrect (Number of particles in unit cells are not the same).
- **Statement D**: Incorrect (FCC is not greater than SCP; they are equal).

### Correct Answers
The correct statements are A and B.

---