To solve the question regarding the number of elements among Zr (Zirconium), Ga (Gallium), Ti (Titanium), Ge (Germanium), B (Boron), and Si (Silicon) for which zone refining can be used, we will follow these steps:
### Step 1: Understand Zone Refining
Zone refining is a method used to purify crystalline solids, particularly semiconductors and some metals. It involves creating a narrow molten zone that moves along a solid rod, allowing impurities to concentrate at one end, which can then be cut off.
**Hint:** Remember that zone refining is primarily used for semiconductors and certain metals.
### Step 2: Identify the Elements
The elements listed are:
- Zr (Zirconium)
- Ga (Gallium)
- Ti (Titanium)
- Ge (Germanium)
- B (Boron)
- Si (Silicon)
**Hint:** Classify these elements based on their properties (metals, semiconductors).
### Step 3: Classify the Elements
- **Zirconium (Zr)**: Metal, not typically refined using zone refining.
- **Gallium (Ga)**: Metal, can be refined using zone refining.
- **Titanium (Ti)**: Metal, not typically refined using zone refining.
- **Germanium (Ge)**: Semiconductor, can be refined using zone refining.
- **Boron (B)**: Semiconductor, can be refined using zone refining.
- **Silicon (Si)**: Semiconductor, can be refined using zone refining.
**Hint:** Focus on identifying which of these elements are semiconductors.
### Step 4: Count the Elements Suitable for Zone Refining
From the classification:
- Gallium (Ga)
- Germanium (Ge)
- Boron (B)
- Silicon (Si)
The elements suitable for zone refining are Ga, Ge, B, and Si.
**Hint:** Make sure to double-check the properties of each element to confirm their classification.
### Step 5: Final Count
The total number of elements for which zone refining can be used is **4** (Ga, Ge, B, Si).
**Final Answer:** The number of elements for which zone refining can be used is **4**.
