1. General Information
- Symbol: P
- Atomic Number: 15
- Atomic Mass: 30.97 u
- Group: 15 (Pnictogens)
- Period: 3
- Block: p-block
- Electron Configuration: 1s² 2s² 2p⁶ 3s² 3p³
- Valence Electrons: 5
- Phase at Room Temperature: Solid
2. Isotopes of Phosphorus
| Isotope |
Protons |
Neutrons |
Abundance |
Notes |
| ³¹P |
15 |
16 |
100% |
Only stable isotope. |
| ³²P |
15 |
17 |
Trace |
Radioactive, used in medicine. |
3. Physical Properties
- Color/Allotropes:
- White Phosphorus (Waxy, Yellow): Highly reactive and toxic.
- Red Phosphorus: Stable, non-toxic, used in safety matches.
- Black Phosphorus: Conductive, layered structure.
- Odor: Odorless (except white phosphorus, which smells like garlic).
- Density: ~1.82 g/cm³ (white phosphorus)
- Melting Point: 44.1°C (white phosphorus)
- Boiling Point: 280°C
- State at STP: Solid
4. Chemical Properties
- Highly Reactive (White Phosphorus):
- Ignites spontaneously in air.
- Stored underwater to prevent oxidation.
- Red and Black Phosphorus are less reactive.
- Forms Covalent Compounds:
- Bonds with oxygen, hydrogen, halogens, and metals.
Reaction with Oxygen:
P₄ + 5O₂ → P₄O₁₀ (Phosphorus Pentoxide)
Reaction with Halogens:
2P + 3Cl₂ → 2PCl₃ (Phosphorus Trichloride)
5. Occurrence and Abundance
- 11th most abundant element in Earth’s crust.
- Not found in free state – Present in minerals.
- Common Minerals:
- Apatite (Ca₅(PO₄)₃(F,Cl,OH))
- Phosphorite (Sedimentary rock containing phosphorus).
6. Industrial Production of Phosphorus
7. Uses of Phosphorus
| Application |
Description |
| Fertilizers |
Phosphates (P₂O₅) promote plant growth. |
| Matches and Fireworks |
Red phosphorus used in match tips and fireworks. |
| Detergents |
Phosphates soften water and remove stains. |
| Steel Production |
Phosphorus improves strength and hardness. |
| Pesticides and Herbicides |
Organophosphates control pests. |
| LEDs and Semiconductors |
Phosphorus used in electronics. |
8. Important Phosphorus Compounds
| Compound |
Formula |
Use |
| Phosphoric Acid |
H₃PO₄ |
Fertilizers, soft drinks. |
| Phosphorus Pentoxide |
P₄O₁₀ |
Drying agent, desiccant. |
| Phosphorus Trichloride |
PCl₃ |
Chemical synthesis, pesticides. |
| Calcium Phosphate |
Ca₃(PO₄)₂ |
Fertilizers, animal feed. |
| Sodium Triphosphate |
Na₅P₃O₁₀ |
Water softener in detergents. |
9. Biological Importance of Phosphorus
- Essential for Life:
- Key component of DNA, RNA, and ATP (energy molecule).
- Present in bones and teeth as calcium phosphate.
- Cell Membranes: Phospholipids form cellular membranes.
- Nutrient for Plants: Supports root development and flowering.
10. Phosphorus in Environmental Chemistry
- Phosphorus Cycle:
- Cycles through soil, plants, animals, and water.
- Excess phosphorus from fertilizers can cause eutrophication (algal blooms).
- Soil Enrichment: Phosphorus fertilization increases crop yields.
11. Safety and Hazards
- White Phosphorus:
- Highly Toxic and Flammable.
- Can cause severe burns upon contact.
- Exposure to Air: Ignites at ~30°C.
- Red Phosphorus:
- Stable and non-toxic but can ignite under friction.
- Inhalation of Phosphorus Vapors can lead to “phossy jaw” (bone decay).
Handling Precautions:
- Store white phosphorus underwater or inert gas.
- Use protective gloves and goggles when handling phosphorus.
Fun Facts About Phosphorus:
- Discovered in 1669 by Hennig Brand while distilling urine.
- Phosphorescence is not caused by phosphorus, despite the name.
- White phosphorus glows in the dark (chemiluminescence).
- Essential for agriculture, yet overuse can harm water ecosystems.