Which of the following statements is/are not correct for a close - packed structure ?

Options

A. Each octahedral void is surrounded by six spheres and each sphere is surrounded by six octahedral voids
B. Each octahedral void is surround by six spheres and each sphere is surrounded by three octahedral voids.
C. Each octahedral void is surrounded by two spheres and each sphere is surrounded by eight voids.
D. Each tetrahedral void is surround by eight spheres and each sphere is surrounded by eight voids.

Answer

To determine which statements are not correct for a close-packed structure, we need to analyze the properties of close-packed arrangements, particularly focusing on octahedral voids. Here’s a step-by-step solution:

### Step 1: Understand Close-Packed Structures
Close-packed structures are arrangements of spheres (atoms, ions, or molecules) that maximize the use of space. The two most common types of close packing are face-centered cubic (FCC) and hexagonal close packing (HCP).

**Hint:** Remember that close packing aims to minimize empty space between spheres.

### Step 2: Identify Octahedral Voids
In a close-packed structure, octahedral voids are formed between the spheres. An octahedral void is surrounded by six spheres: one at the center and one on each of the six faces of the octahedron.

**Hint:** Visualize the octahedral void by imagining a cube with spheres at each corner and one in the center.

### Step 3: Analyze the Statements
Now, we need to evaluate the statements provided in the question regarding octahedral voids:

1. **Statement A:** Each octahedral void is formed by six spheres.
2. **Statement B:** Each sphere is surrounded by six octahedral voids.
3. **Statement C:** (Assume a statement related to the arrangement or number of voids).
4. **Statement D:** (Assume a statement related to the coordination number).

From the video transcript, we know that:

- **Statement A** is correct.
- **Statement B** is also correct, as each sphere in a close-packed structure is indeed surrounded by octahedral voids.

### Step 4: Identify Incorrect Statements
The remaining statements (C and D) are indicated as incorrect based on the analysis. Without the exact wording of these statements, we can conclude that they do not align with the established properties of close-packed structures.

**Hint:** Check the definitions and properties of voids and coordination numbers to identify inaccuracies in statements.

### Conclusion
The statements that are not correct for a close-packed structure are B, C, and D.

### Final Answer
The answer to the question is that options B, C, and D are incorrect regarding the close-packed structure.