Aluminum
Atomic Data
| Atomic Number | 13 |
| Symbol | Al |
| Atomic Weight | 26.982 u |
| Density (STP) | 2.7 g/cm³ |
| Melting Point | 660.32 °C (933.47 K) |
| Boiling Point | 2518.85 °C (2792 K) |
| Electronegativity | 1.61 (Pauling) |
| Electron Config. | 1s2 2s2 2p6 3s2 3p1 |
| Oxidation States | +3 |
| Phase at STP | Solid |
| Category | Post-Transition Metal |
| Period / Group | 3 / 13 |
| CAS Number | 7429-90-5 |
Electron Configuration
[Ne] 3s2 3p1
| Shell | n | Subshell | Electrons | Cumulative |
|---|---|---|---|---|
| K | 1 | 1s | 2 | 2 |
| L | 2 | 2s | 2 | 4 |
| L | 2 | 2p | 6 | 10 |
| M | 3 | 3s | 2 | 12 |
| M | 3 | 3p | 1 | 13 |
| Total | 13 | 13 | ||
Isotopes of Aluminum
Aluminum is monoisotopic: ²⁷Al is its only naturally occurring stable isotope, accounting for 100% of all natural Aluminum.
| Isotope | Symbol | Protons | Neutrons | Abundance | Stability |
|---|---|---|---|---|---|
| Aluminum-27 | ²⁷Al | 13 | 14 | 100% | Stable |
Abundance & Occurrence
Aluminum is present in Earth's crust at approximately 82300 ppm by mass and at approximately 58 ppm by mass throughout the universe.
Earth's Crust (ppm by mass)
Universe (ppm by mass)
Discovery & History
Read more about the discovery of the periodic table of elements →
Safety & Handling
- General toxicity: Bulk aluminum metal is generally regarded as non-toxic and is used safely in food packaging, cookware, and beverage cans. Regulatory bodies have established acceptable daily intake levels for aluminum from all sources.
- Dust and powder hazard: Finely divided aluminum dust or powder is highly flammable and can form explosive mixtures with air. Industrial processes that generate aluminum dust require careful ventilation, ignition control, and explosion suppression systems.
- Inhalation risk: Prolonged occupational inhalation of aluminum dust or fumes can cause pulmonary fibrosis (aluminosis). Appropriate respiratory protection: including P100 respirators or supplied-air equipment: is required in grinding, polishing, and smelting operations.
- Reactivity with acids and bases: Aluminum dissolves in strong acids (e.g., hydrochloric acid) and strong bases (e.g., sodium hydroxide), releasing hydrogen gas. Hydrogen is flammable; work near these reactions should be conducted away from ignition sources.
- Storage: Aluminum powder and flakes must be stored in tightly sealed, moisture-free containers away from oxidisers, halogens, and strong acids. Bulk aluminum stock is stable under normal conditions and requires no special storage precautions.
Aluminum in the Real World
Real-World Uses
- Packaging foil and cans: Aluminum's impermeability to light, oxygen, and moisture makes it the dominant material for food and beverage packaging; it is endlessly recyclable with only about 5% of the energy required for primary production.
- Aircraft and vehicle structures: Aluminum alloys such as 2024 and 7075 offer a strength-to-weight ratio competitive with steel, making them essential in aircraft fuselages, wings, car body panels, and space launch vehicle structures.
- Electrical power lines: Aluminum conducts electricity at roughly 61% of copper's conductivity but at one-third the weight, making it the preferred conductor for long-distance overhead transmission lines where weight and cost matter more than maximum conductivity.
- Building construction: Window frames, curtain walls, roofing, and structural cladding use aluminum extrusions and sheets because of their corrosion resistance, low maintenance requirements, and ease of forming into complex profiles.
- Kitchenware: Aluminum's excellent thermal conductivity, light weight, and low cost make it standard for pots, pans, baking trays, and foil wrap used in domestic and commercial kitchens worldwide.
Downloadable Resources
Free periodic table reference sheets for classrooms, study sessions, and laboratory use.
Frequently Asked Questions
What is aluminum used for?
Aluminum is used in packaging foil and cans, aircraft and vehicle structures, electrical power transmission lines, building construction, and kitchenware. Its combination of low density, high strength, and corrosion resistance makes it one of the most widely applied metals in modern industry.
Is aluminum toxic to humans?
Aluminum in its bulk metallic form is generally considered non-toxic and is used safely in cookware and food packaging. However, fine aluminum dust or powder can be harmful if inhaled and poses a flammability and explosion risk in industrial settings. Some research has investigated potential links between high aluminum exposure and neurological effects, but no definitive causal relationship has been established.
Why is aluminum so lightweight?
Aluminum has a density of only 2.7 g/cm³, roughly one-third that of steel, because its atoms are relatively light (atomic weight 26.982 u) and pack into a face-centred cubic crystal structure with moderate spacing. This low density combined with good tensile strength is why aluminum is favoured in aerospace and transportation applications.
Who discovered aluminum and when?
Aluminum was first isolated in impure form by Danish chemist Hans Christian Ørsted in 1825 by reducing aluminum chloride with potassium amalgam. German chemist Friedrich Wöhler produced purer samples in 1827. Commercial production became practical in 1886 when Charles Martin Hall and Paul Héroult independently developed the electrolytic Hall–Héroult process, which remains the primary production method today.
Does aluminum rust?
Aluminum does not rust in the way iron does, because it lacks iron. Instead, aluminum reacts with oxygen in the air to form a thin, hard layer of aluminum oxide (Al₂O₃) that tightly adheres to the surface and prevents further oxidation. This self-passivating behaviour makes aluminum naturally corrosion-resistant without the need for protective coatings in most environments.