Quick Facts
| Property | Value |
|---|---|
| Symbol | P |
| Atomic Number | 15 |
| Atomic Mass | 30.974 u |
| Category | Nonmetal |
| Period | 3 |
| Group | 15 |
| Block | p |
| Electron Configuration | [Ne] 3s² 3p³ |
Physical Properties
| Property | Value |
|---|---|
| State at 20°C | Solid |
| Density | 1.82 g/cm³ (white), 2.69 g/cm³ (red) |
| Melting Point | 44.15°C (317.3 K) white P |
| Boiling Point | 280.5°C (553.7 K) |
| Appearance | White (waxy), red, or black solid |
Atomic Properties
| Property | Value |
|---|---|
| Electron Configuration | [Ne] 3s² 3p³ |
| Electronegativity | 2.19 (Pauling scale) |
| First Ionization Energy | 1011.8 kJ/mol |
| Atomic Radius | 110 pm |
| Covalent Radius | 107 pm |
| Van der Waals Radius | 180 pm |
History and Discovery
Discovered by: Hennig Brand Year of Discovery: 1669 Location: Hamburg, Germany
Etymology
The name "phosphorus" comes from the Greek "phosphoros" meaning "light-bearing," from "phos" (light) and "phoros" (bearer). This refers to its property of glowing in the dark.
Discovery Story
Hennig Brand discovered phosphorus in 1669 while attempting to create the philosopher's stone from urine. He heated and processed large quantities of urine, eventually producing a glowing white waxy substance. This was the first element discovered in modern times. Robert Boyle independently discovered it in 1680 and published the method.
Isotopes
| Isotope | Natural Abundance | Half-life | Decay Mode |
|---|---|---|---|
| ³¹P | 100% | Stable | - |
| ³²P | Synthetic | 14.3 days | β⁻ |
| ³³P | Synthetic | 25.3 days | β⁻ |
Occurrence
Natural Abundance
Phosphorus comprises about 1,050 ppm of Earth's crust and is the 11th most abundant element. It never occurs free in nature due to its reactivity. Major sources are phosphate rocks, mainly apatite (Ca₅(PO₄)₃(F,Cl,OH)). Significant deposits are found in Morocco, China, and the United States.
Extraction and Production
- Thermal Process: Heating phosphate rock with coke and silica in electric furnaces
- Wet Process: Treating phosphate rock with sulfuric acid (for fertilizers)
- Sources: Phosphate rock mining
- Global production: about 250 million tons of phosphate rock annually
Applications and Uses
Agricultural Applications
- Fertilizers (phosphates are essential for plant growth)
- Animal feed supplements
- Soil amendments
Industrial Applications
- Matches and incendiary devices (red phosphorus)
- Steel production (phosphoric acid)
- Water treatment
- Cleaning products
Chemical Applications
- Phosphoric acid (soft drinks, food additive)
- Organophosphate pesticides
- Flame retardants
- Plasticizers
Other Uses
- Fireworks and flares
- Phosphor screens (CRT displays)
- Semiconductor doping
Biological Role
Phosphorus is essential for life. It is a component of DNA, RNA, ATP, and cell membranes (phospholipids).
In the Human Body
- About 1% of body mass (700 g in adult)
- 85% in bones and teeth as calcium phosphate
- Essential for energy metabolism (ATP)
- Component of DNA and RNA backbone
- Daily requirement: 700 mg
Dietary Sources
Meat, dairy products, eggs, fish, nuts, and legumes are rich in phosphorus.
Safety and Hazards
Toxicity
White phosphorus is extremely toxic and can cause severe burns and organ damage. Red and black phosphorus are much safer.
Handling Precautions
- White phosphorus ignites spontaneously in air (pyrophoric)
- White phosphorus stored under water
- Causes severe chemical burns on skin contact
- Highly toxic if ingested (lethal dose ~50 mg)
- Red phosphorus is much safer but can convert to white if heated
Environmental Impact
Phosphate runoff from agriculture causes eutrophication of water bodies. Phosphorus is a limiting nutrient in many ecosystems.
Interesting Facts
- The "phosphorescent" glow of white phosphorus is actually chemiluminescence from slow oxidation
- Matches contain red phosphorus on the striking surface, not in the match head
- ATP (adenosine triphosphate), the energy currency of cells, contains three phosphate groups
- "Phossy jaw" was an occupational disease of match workers caused by white phosphorus exposure
- Phosphorus was used in early motion picture film and caused many theater fires