in which of the following arrangement octahedral voids are formed ?

Options

A. hcp
B. bcc
C. simple cubic
D. fcc

Explanation

To determine in which arrangements octahedral voids are formed, we need to analyze the different types of crystal structures mentioned in the question: Face-Centered Cubic (FCC), Body-Centered Cubic (BCC), Simple Cubic, and Face-Centered Pentagonal (FCP).

### Step-by-Step Solution:

1. **Understanding Octahedral Voids**:
- An octahedral void is a type of interstitial site in a crystal lattice where a smaller atom can fit between larger atoms. In a three-dimensional arrangement, octahedral voids are formed when atoms are positioned in such a way that they create an octahedron shape around the void.

2. **Analyzing Crystal Structures**:
- **Face-Centered Cubic (FCC)**: In FCC, atoms are located at each corner and the centers of all the faces of the cube. In this arrangement, octahedral voids are present at the center of the cube and at the edge centers. Therefore, FCC has octahedral voids.

- **Body-Centered Cubic (BCC)**: In BCC, there is one atom at each corner of the cube and one atom at the center of the cube. BCC also has octahedral voids, which are located at the edges of the cube. Thus, BCC has octahedral voids as well.

- **Simple Cubic**: In a simple cubic arrangement, there is one atom at each corner of the cube, and there are no octahedral voids present in this structure.

- **Face-Centered Pentagonal (FCP)**: The FCP arrangement is less common, but it can also form octahedral voids similar to FCC.

3. **Conclusion**:
- From the analysis, we can conclude that octahedral voids are formed in FCC and BCC arrangements. Therefore, the correct options are FCC and BCC.

### Final Answer:
- Octahedral voids are formed in **FCC** and **BCC** arrangements.