Quick Facts
| Property | Value |
|---|---|
| Symbol | Al |
| Atomic Number | 13 |
| Atomic Mass | 26.982 u |
| Category | Post-Transition Metal |
| Period | 3 |
| Group | 13 |
| Block | p |
| Electron Configuration | [Ne] 3s² 3p¹ |
Physical Properties
| Property | Value |
|---|---|
| State at 20°C | Solid |
| Density | 2.70 g/cm³ |
| Melting Point | 660.32°C (933.47 K) |
| Boiling Point | 2519°C (2792 K) |
| Appearance | Silvery-white, soft metal |
Atomic Properties
| Property | Value |
|---|---|
| Electron Configuration | [Ne] 3s² 3p¹ |
| Electronegativity | 1.61 (Pauling scale) |
| First Ionization Energy | 577.5 kJ/mol |
| Atomic Radius | 143 pm |
| Covalent Radius | 121 pm |
| Van der Waals Radius | 184 pm |
History and Discovery
Discovered by: Hans Christian Ørsted Year of Discovery: 1825 Location: Copenhagen, Denmark
Etymology
The name "aluminum" (or "aluminium" in British English) comes from "alum," a compound known since antiquity. The Latin "alumen" means "bitter salt."
Discovery Story
Hans Christian Ørsted first produced impure aluminum in 1825 by reducing aluminum chloride with potassium amalgam. Friedrich Wöhler refined the process in 1827 and is often credited with the discovery. Henri Sainte-Claire Deville developed the first commercial production in 1856. The Hall-Héroult process (1886) made aluminum economically viable.
Isotopes
| Isotope | Natural Abundance | Half-life | Decay Mode |
|---|---|---|---|
| ²⁷Al | 100% | Stable | - |
| ²⁶Al | Trace | 717,000 years | β⁺ |
Occurrence
Natural Abundance
Aluminum is the most abundant metal in Earth's crust (about 8.1%) and third most abundant element overall. It is never found free in nature. Major ores include bauxite (Al₂O₃·xH₂O), cryolite, and various clay minerals.
Extraction and Production
- Bayer Process: Extraction of alumina (Al₂O₃) from bauxite
- Hall-Héroult Process: Electrolysis of alumina in molten cryolite
- Recycling: Secondary aluminum from recycled material (requires 5% of primary production energy)
- Global production: about 65 million tons annually
Applications and Uses
Construction and Transportation
- Building facades and window frames
- Aircraft structures and components
- Automotive body panels and engine parts
- Bridges and infrastructure
Packaging
- Beverage cans
- Foil for food preservation
- Blister packs
Electrical
- Power transmission lines (lighter than copper)
- Heat sinks for electronics
- LED housings
Other Uses
- Cookware and kitchen utensils
- Mirrors and reflectors
- Fireworks (produces silver sparks)
- Thermite welding
Biological Role
Aluminum has no known biological function and is not essential for life. The human body has developed no mechanisms to utilize it.
In the Human Body
- Small amounts present (about 50-150 mg)
- Poorly absorbed from food
- Excreted efficiently by healthy kidneys
Health Concerns
High aluminum exposure has been studied in relation to neurological conditions, though direct causation remains controversial.
Safety and Hazards
Toxicity
Aluminum is considered low-toxicity. However, high exposures can be harmful, especially for those with kidney impairment.
Handling Precautions
- Fine aluminum powder is flammable and can explode
- Molten aluminum reacts violently with water
- Aluminum dust requires proper ventilation
- Use appropriate protective equipment during grinding/machining
Environmental Impact
Bauxite mining can cause habitat destruction and water pollution. Aluminum production is energy-intensive (about 2% of global electricity). Recycling is highly beneficial.
Interesting Facts
- Aluminum was once more valuable than gold—Napoleon III served his most honored guests with aluminum utensils
- The Washington Monument is capped with an aluminum apex, installed when aluminum was still precious (1884)
- It takes about 4 kg of bauxite to make 1 kg of aluminum
- Recycling aluminum saves 95% of the energy needed for primary production
- Aluminum forms a thin oxide layer instantly when exposed to air, preventing further corrosion