Aluminum
Definition and meaning of Aluminum in chemistry.
![Aluminum element card: symbol Al, atomic number 13, atomic mass 26.982, electron configuration [Ne] 3s² 3p¹, oxidation states +3, Post-transition metal, group 13, period 3, solid at room temperature.](/assets/images/terms/aluminum-chemical-element.webp)
Aluminum is a lightweight, silvery-white metal with atomic number 13. It is the most abundant metal in Earth's crust and the third most abundant element overall. Aluminum is valued for its strength-to-weight ratio, conductivity, and natural resistance to corrosion.
In more detail
When exposed to air, aluminum quickly forms a thin protective layer of aluminum oxide on its surface. This oxide layer is dense and tightly bonded, so it blocks oxygen from reaching the metal underneath. This sets aluminum apart from iron, whose rust layer is porous and allows corrosion to continue.
Because aluminum combines low density with strong corrosion resistance, it is widely used in aircraft, cars, and building construction. It also conducts electricity and heat efficiently, making it valuable for power transmission lines and electronic devices. By volume, though, aluminum is a less efficient electrical conductor than copper.
Commercial aluminum comes almost entirely from bauxite ore. Producers first refine bauxite into pure aluminum oxide through the Bayer process. They then convert that oxide into metallic aluminum using electrolysis in the Hall-Héroult process, which requires large amounts of electrical energy.
Aluminum is also nontoxic and lightweight, which makes it useful for packaging, cookware, and beverage cans. Pure aluminum is relatively soft, so most practical applications use aluminum alloys instead. These are mixtures with small amounts of other metals, like copper, magnesium, or silicon, that increase strength while keeping the material light. These alloys are classified by a numbering system that identifies their main alloying elements and typical properties.
Key facts
| Atomic number | 13 |
|---|---|
| Chemical symbol | Al |
| Density | 2.70 g/cm³ at room temperature |
| Field | Inorganic Chemistry |
| Primary ore | Bauxite |
| Extraction process | Bayer process, then Hall-Héroult electrolysis |
Aluminum foil works well for cooking and food storage because it is flexible, distributes heat evenly, and forms a protective oxide layer on its surface. This coating keeps the reactive metal from directly contacting and reacting with food.
Frequently asked questions
Why doesn't aluminum rust like iron?
Aluminum forms a thin, dense oxide coating instantly when exposed to oxygen, creating a protective barrier that prevents further oxidation. Iron oxide (rust), by contrast, is porous, allowing continued corrosion of the underlying metal.
What is bauxite and where does it come from?
Bauxite is the primary ore from which commercial aluminum is extracted. It is an aluminum oxide mineral found mostly in tropical and subtropical regions, with major deposits in Australia, Guinea, and Brazil.
Why is aluminum recycling so energy-efficient?
Recycling aluminum only requires melting the existing metal, which uses about 5 percent of the energy needed to extract new aluminum from bauxite ore through electrolysis. This makes aluminum one of the most cost-effective materials to recycle.
Related terms
Sources & references
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