Which of the following structure is most uncommon for metals? 

Options

A. simple cubic
B. B.C.C.
C. C.C.P
D. H.C.P

Answer

To determine which structure is the most uncommon for metals among the given options (simple cubic, BCC, CCP, and HCP), we can analyze each structure based on their prevalence in metallic elements.

### Step-by-Step Solution:

1. **Understanding the Structures**:
- **Simple Cubic (SC)**: In this structure, atoms are located at the corners of a cube. Each unit cell has 1 atom.
- **Body-Centered Cubic (BCC)**: In this structure, atoms are located at the corners of a cube with one atom in the center. Each unit cell has 2 atoms.
- **Cubic Close-Packed (CCP)**: Also known as face-centered cubic (FCC), this structure has atoms at each corner and the centers of each face of the cube. Each unit cell has 4 atoms.
- **Hexagonal Close-Packed (HCP)**: This structure has a hexagonal arrangement with layers of atoms. Each unit cell has 6 atoms.

2. **Identifying Common Structures for Metals**:
- **BCC**: Common examples include sodium, potassium, and cesium.
- **CCP (FCC)**: Common examples include copper, gold, and platinum.
- **HCP**: Common examples include beryllium and zinc.

3. **Analyzing the Rarity of Simple Cubic**:
- The simple cubic structure is quite uncommon for metals. The only metals that exhibit this structure are manganese and polonium, making it rare compared to the other structures.

4. **Conclusion**:
- Among the options provided, the **simple cubic structure** is the most uncommon for metals.

### Final Answer:
The most uncommon structure for metals is **simple cubic**.

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