Which of the following statement(s) is incorrect?

Options

A. The coordination number of each type of ion in CsCl crystal is 8
B. A metal that crystallizes in bcc structure has a coordination number of 12
C. A unit cell of an ionic crystal shares some of its ions with other unit cells
D. The length of the unit cell in NaCl is 552 pm `(r_(Na^+)=95"pm",r_(Cr^-)=181"pm")`

Answer

To determine which of the following statements is incorrect, we will analyze each option one by one.

### Step-by-Step Solution:

1. **Analyze Option A**:
- Statement: "The coordination number of each type of ion in CsCl crystal is 8."
- **Explanation**: CsCl (cesium chloride) has a body-centered cubic (BCC) structure. In this structure, each Cs⁺ ion is surrounded by 8 Cl⁻ ions and vice versa. Therefore, the coordination number for both ions is indeed 8.
- **Conclusion**: Option A is **correct**.

2. **Analyze Option B**:
- Statement: "Metal has a crystal in BCC structure has coordination number 12."
- **Explanation**: In a body-centered cubic (BCC) structure, the coordination number is 8, not 12. The coordination number of 12 is characteristic of face-centered cubic (FCC) structures.
- **Conclusion**: Option B is **incorrect**.

3. **Analyze Option C**:
- Statement: "The unit cell of an ionic crystal shares some of its ions with other unit cells."
- **Explanation**: In ionic crystals, ions at the edges and corners of the unit cell are shared with adjacent unit cells. This is a characteristic feature of ionic crystals.
- **Conclusion**: Option C is **correct**.

4. **Analyze Option D**:
- Statement: "The length of a unit cell in NaCl is given by a specific formula."
- **Explanation**: The unit cell length (A) in NaCl can be derived from the radii of the ions. The relationship is given by the equation \( r_{Na^+} + r_{Cl^-} = \frac{A}{2} \). This is consistent with the structure of NaCl.
- **Conclusion**: Option D is **correct**.

### Final Conclusion:
- The only incorrect statement among the options is **Option B**.