Of the different allotropes of phosphorus, the one which is most reactive is

Options

A. Violet phosphorus
B. Scarlet phosphorus
C. Red phosphorus
D. White phosphorus

Answer

To determine which allotrope of phosphorus is the most reactive, we can analyze the properties of the different allotropes of phosphorus: white phosphorus, red phosphorus, and black phosphorus.

### Step-by-Step Solution:

1. **Identify the Allotropes of Phosphorus**:
- The main allotropes of phosphorus are white phosphorus, red phosphorus, and black phosphorus. Each allotrope has distinct structural and chemical properties.

2. **Understand the Structure of Each Allotrope**:
- **White Phosphorus (P4)**: Consists of tetrahedral P4 molecules. It is highly reactive and unstable due to its strain and the presence of weak P-P bonds.
- **Red Phosphorus**: Has a network structure and is more stable than white phosphorus. It is less reactive due to its stronger P-P bonds.
- **Black Phosphorus**: Has a layered structure similar to graphite and is the least reactive among the allotropes.

3. **Analyze Reactivity**:
- Reactivity is often related to stability; the less stable an allotrope is, the more reactive it tends to be.
- White phosphorus is known for its high reactivity and is often used in pyrotechnics and as a chemical reagent.

4. **Conclusion**:
- Based on the analysis, white phosphorus is the most reactive allotrope of phosphorus due to its unstable structure and high energy state.

### Final Answer:
The most reactive allotrope of phosphorus is **white phosphorus**.