The allotrope of phosphorous obtained by heating white phosphorous to 473 K is 

Options

A. `alpha-`balck
B. `beta-` black
C. red
D. scarlet

Answer

To solve the question regarding the allotrope of phosphorus obtained by heating white phosphorus to 473 K, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Allotropes of Phosphorus**:
- Phosphorus has several allotropes, including white phosphorus (P4), red phosphorus, and black phosphorus (which can be further divided into alpha and beta forms).

2. **Understand the Process**:
- The question specifies heating white phosphorus (P4) to 473 K. This process typically involves applying high pressure as well.

3. **Determine the Resulting Allotrope**:
- When white phosphorus is heated to 473 K under high pressure, it transforms into a different allotrope. The specific allotrope formed in this condition is known as beta black phosphorus.

4. **Explain the Structure**:
- The structure of beta black phosphorus is different from that of white phosphorus. While white phosphorus has a tetrahedral P4 structure, beta black phosphorus has a layered structure resembling graphite, where phosphorus atoms are arranged in sheets.

5. **Conclusion**:
- Therefore, the allotrope of phosphorus obtained by heating white phosphorus to 473 K is beta black phosphorus.

### Final Answer:
The allotrope of phosphorus obtained by heating white phosphorus to 473 K is **beta black phosphorus**.

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