The correct statement about, CCP structure is

Options

A. Packing fraction = 26%
B. Coordination number = 6
C. Unit cell is face centred cubic
D. AB - AB type of packing

Answer

To determine the correct statement about the CCP (Cubic Closed Packing) structure, we need to analyze each of the given options based on our knowledge of solid-state chemistry.

### Step-by-Step Solution:

1. **Understanding CCP Structure**:
- CCP, or Cubic Closed Packing, is a type of crystal structure where spheres are packed in a three-dimensional arrangement. It is also known as Face-Centered Cubic (FCC) structure.

2. **Analyzing the Options**:
- **Option 1**: Packing fraction is 26%.
- **Analysis**: The packing fraction for CCP (FCC) is actually 74%, not 26%. Therefore, this statement is incorrect.

- **Option 2**: Coordination number is equal to 6.
- **Analysis**: In a CCP structure, the coordination number is 12, meaning each atom is in contact with 12 other atoms. Thus, this statement is also incorrect.

- **Option 3**: Unit cell is face-centered cubic.
- **Analysis**: This is true. The unit cell of CCP is indeed face-centered cubic (FCC).

- **Option 4**: ABAB type of packing.
- **Analysis**: The packing in CCP is actually ABCABC type, not ABAB. Therefore, this statement is incorrect.

3. **Conclusion**:
- The only correct statement about the CCP structure is **Option 3: Unit cell is face-centered cubic**.

### Final Answer:
The correct statement about CCP structure is that the unit cell is face-centered cubic (FCC).

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