Allotropes of Phosphorus
Preparation, Properties, Structure, Uses and Previous Year Questions
Highly Important for NEET, IIT-JEE, IIT-JAM, GATE & CSIR-NET
Definition: Different structural modifications of phosphorus that exist in more than one crystalline or amorphous forms. Phosphorus exhibits the greatest number of allotropes among all elements.
Major Allotropes of Phosphorus
1. White Phosphorus
White Phosphorus: Preparation, Properties, Structure and Uses
White Phosphorus PYQs MCQs
2. Red Phosphorus
Red Phosphorus: Preparation, Properties, Structure and Uses
Red Phosphorus PYQs MCQs
3. Black Phosphorus
Black Phosphorus: Preparation, Properties, Structure and Uses
Black Phosphorus PYQs MCQs
Structure of White, Red and Black Phosphorus
Other Allotropes
- Violet Phosphorus: Intermediate between white and red phosphorus
- Metastable Black Phosphorus: Formed by laser irradiation of red phosphorus
- Fibrous Phosphorus: Intermediate form between white and red phosphorus
Comparison of Major Allotropes
| Property | White Phosphorus | Red Phosphorus | Black Phosphorus |
|---|---|---|---|
| Structure | Tetrahedral P4 molecules | Polymeric chains | Layered orthorhombic |
| Appearance | Waxy white solid | Dark red powder | Black crystalline solid |
| Reactivity | Highly reactive | Less reactive | Least reactive |
| Ignition Temperature | 30°C | 260°C | 450°C |
| Density (g/cm³) | 1.82 | 2.20-2.35 | 2.69 |
| Stability | Least stable | Moderately stable | Most stable |