- Aluminium (Al) is a silvery-white, lightweight metal with atomic number 13, positioned in Group 13 of the periodic table.
- It has three valence electrons in its outermost shell, giving it a stable +3 oxidation state in most compounds.
- Its atomic structure consists of thirteen protons, typically fourteen neutrons, and thirteen electrons arranged in three shells (two in the first shell, eight in the second, and three in the third).
- Aluminium has only one naturally occurring isotope, aluminium-27 (²⁷Al), which is stable, although the radioactive isotope aluminium-26 (²⁶Al) occurs in trace amounts from cosmic ray interactions and is used in geological dating.
- Under standard conditions, aluminium is solid, lightweight, and has a bright metallic luster that quickly becomes coated with a thin, protective oxide layer upon exposure to air.
- Aluminium is the most abundant metal in Earth’s crust and the third most abundant element overall, after oxygen and silicon, making up about 8.23% by mass. However, it does not occur naturally in its pure metallic form due to its high reactivity with oxygen; instead, it is found in minerals such as bauxite (a mixture of aluminium hydroxides), cryolite (Na₃AlF₆), and feldspar. Commercial production is primarily achieved via the Bayer process, which refines bauxite into alumina (Al₂O₃), followed by electrolytic reduction through the Hall–Héroult process to obtain pure aluminium.
- Although compounds of aluminium, such as alum (potassium aluminium sulfate), were known in antiquity and used in dyeing and tanning, metallic aluminium was first isolated in 1825 by Danish chemist Hans Christian Ørsted. Friedrich Wöhler improved the method in 1827, and by the late 19th century, advances in electrochemistry made aluminium production economical, leading to widespread industrial use.
- Aluminium’s combination of low density, high corrosion resistance, and good conductivity makes it one of the most versatile engineering materials. It is used extensively in aerospace, automotive, packaging (such as beverage cans and foil), construction, electrical transmission lines, and consumer products. Alloying aluminium with elements like copper, magnesium, manganese, silicon, or zinc enhances its mechanical strength while maintaining light weight.
- Chemically, aluminium forms a thin, adherent oxide layer (Al₂O₃) in air, which protects it from further oxidation—a property known as passivation. It reacts with acids to form aluminium salts and hydrogen gas, and with strong bases to produce aluminates, due to its amphoteric nature. Aluminium readily forms covalent and ionic compounds, including a wide variety of oxides, hydroxides, and complex salts.
- Biologically, aluminium has no known essential role in living organisms and is generally considered non-toxic in small amounts. However, excessive exposure, especially in industrial settings or through certain water treatment processes, can have potential health effects, and its possible links to neurological disorders are still under investigation. In contrast, aluminium compounds are widely used safely in products such as antacids, food additives, and antiperspirants.
