Aluminium
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
1s2 2s2 2p6 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 Aluminium
Aluminium has only one naturally occurring isotope, 27Al, which accounts for 100% of all natural aluminium and is entirely stable. This monoisotopic nature makes aluminium extremely useful in NMR spectroscopy and mass spectrometry.
| Isotope | Symbol | Protons | Neutrons | Abundance | Stability |
|---|---|---|---|---|---|
| Aluminium-27 | ⁷²Al | 13 | 14 | 100% | Stable |
Abundance & Occurrence
Aluminium makes up approximately 8.23% of Earth’s crust by mass, making it the most abundant metal and the third most abundant element on the planet after oxygen and silicon. It is never found as a free metal in nature — it occurs almost exclusively in silicate minerals and in bauxite, a mixture of aluminium hydroxide minerals that serves as the primary commercial ore. Guinea holds the world’s largest proven bauxite reserves, followed closely by Australia and Brazil.
EARTH'S CRUST — ELEMENTS BY MASS
WORLD BAUXITE RESERVES BY COUNTRY
Discovery & History
Safety & Handling
- Generally non-toxic in bulk: Aluminium metal in solid or sheet form poses no significant health risk under normal handling conditions. The digestive system absorbs very little aluminium, and healthy kidneys excrete it efficiently.
- Dust and powder fire and explosion hazard: Finely divided aluminium powder and dust are highly flammable and can form explosive mixtures with air. Thermite reactions (aluminium + iron oxide) burn at over 2500 °C and cannot be extinguished with water — use dry sand or Class D extinguishers.
- Industrial inhalation risk: Prolonged inhalation of aluminium dust or fumes in smelter environments has been linked to pulmonary fibrosis and potential neurological effects. Appropriate respiratory protection (P3 filter) is required in all aluminium production and machining facilities.
- Kidney disease caution: Patients with chronic kidney disease or undergoing dialysis can accumulate aluminium from antacids and dialysate solutions, potentially causing aluminium toxicity including dialysis dementia and softening of the bones (osteomalacia).
- Corrosive compound hazards: Aluminium chloride (AlCl₃) is a strong Lewis acid and skin irritant. Aluminium smelting also produces fluoride gases and polycyclic aromatic hydrocarbons from the Soderberg anode process — engineering controls and PPE are essential.
- Storage: Bulk aluminium ingots and sheet require no special storage. Aluminium powder must be kept in sealed, grounded metal containers away from all ignition sources, oxidisers, acids, and moisture.
Aluminium in the Real World
Real-World Uses
- Packaging foil and cans — Aluminium’s impermeability to gas and moisture, light weight, and non-toxicity make it the dominant material for beverage cans, food packaging foil, and pharmaceutical blister packs. Recycling aluminium uses only about 5% of the energy needed to produce primary metal from ore, making it one of the most economically recycled materials on Earth.
- Aircraft and vehicle structures — Aluminium alloys (particularly the 2xxx, 6xxx, and 7xxx series alloyed with copper, magnesium, and zinc) are the structural backbone of commercial aviation and a major component of automotive body panels and frames. Their high strength-to-weight ratio is critical for fuel efficiency and range.
- Electrical power lines — Aluminium’s electrical conductivity (about 61% of copper by volume but far lighter by weight) makes it the preferred conductor for overhead high-voltage transmission lines. Steel-core aluminium conductor (ACSR) cables carry the majority of the world’s long-distance electricity supply.
- Building and construction — Window frames, curtain walls, roofing panels, structural extrusions, and architectural cladding extensively use aluminium. Its natural self-forming oxide layer provides corrosion resistance without painting or galvanising, and its low maintenance cost suits long-life building elements.
- Kitchenware and cookware — Aluminium’s excellent thermal conductivity (205 W/m·K), light weight, and low cost make it ideal for pots, pans, baking trays, and cooking foil. Anodised and hard-anodised aluminium surfaces are standard in professional cookware for their durability and scratch resistance.
Downloadable Resources
Free periodic table reference sheets for classrooms, study sessions, and laboratory use.
Frequently Asked Questions
Why is aluminium so widely used?
Aluminium combines a low density (2.7 g/cm³) with good strength, excellent corrosion resistance due to its self-forming oxide layer, high thermal and electrical conductivity, and full recyclability. These properties make it the second most used metal in the world after steel, with applications spanning packaging, transport, construction, and electrical infrastructure.
Is aluminium the most abundant metal on Earth?
Yes. Aluminium makes up about 8.23% of Earth’s crust by mass, making it the most abundant metal and the third most abundant element overall after oxygen and silicon. Despite this abundance, it was once rarer than gold because it was so difficult to extract from its ores.
What is the difference between aluminium and aluminum?
Aluminium and aluminum are two spellings for the same element (atomic number 13, symbol Al). “Aluminium” is the IUPAC-preferred international spelling used in the UK, Australia, and most of the world. “Aluminum” is the standard spelling in the United States and Canada. The element was originally named “alumium” by Humphry Davy in 1808 before being standardised.
Is aluminium toxic to humans?
Aluminium is generally considered non-toxic for everyday exposure at normal environmental levels; the body absorbs very little through the gut and excretes it efficiently via the kidneys. However, fine aluminium dust and powder are a serious inhalation and fire hazard in industrial settings. People with kidney disease may accumulate aluminium from antacids or dialysis fluids. Some research investigates links between chronic aluminium exposure and neurological conditions, though no definitive causal relationship has been established.
Who discovered aluminium?
Hans Christian Ørsted first isolated impure aluminium in 1825 by reducing aluminium chloride with potassium amalgam. Friedrich Wöhler produced purer aluminium in 1827. The first practical large-scale production came from Henri Sainte-Claire Deville’s chemical process in 1854. The modern electrolytic Hall–Héroult process, developed independently by Charles Martin Hall and Paul Héroult in 1886, made aluminium affordable and transformed it into an everyday material.