Aluminium

Aluminium, also spelled aluminum in North America, is a chemical element with the symbol Al and atomic number 13. It is a light metal, about one-third as heavy as steel. It is strong and flexible. Aluminium looks shiny and silver-like because it reflects light very well.

This metal does not attract magnets and can be bent easily. It forms a thin, protective layer when it touches air, which helps it last a long time. Aluminium is very common in the world, especially in rocks, where it is the third-most abundant element after oxygen and silicon. We get it from a type of rock called bauxite.

People first learned about aluminium in 1825, and it became easier to make in large amounts in 1886. Since then, it has been used in many things, like cars, buildings, and packages. Even though aluminium is everywhere, living things do not use it for their own processes, but it is safe for plants and animals.

Physical characteristics

Isotopes

Main article: Isotopes of aluminium

Aluminium has one stable isotope, ²⁷Al, which makes up almost all of the aluminium found in nature. All other isotopes of aluminium are radioactive. The most stable one is ²⁶Al, which lasts about 717,000 years. Tiny amounts of it are still made today from the breaking down of argon in the air by cosmic rays.

Electron shell

An aluminium atom has 13 electrons. It can lose three of these electrons when it reacts with other elements. This makes aluminium useful in many chemical processes. Aluminium is a soft metal with a low melting point.

Bulk

Aluminium looks silvery-white to dull gray, depending on its surface. It is very light, weighing about one-third as much as steel for the same size. This lightness makes it perfect for use in airplanes. Pure aluminium is soft, so it is often mixed with other metals to make it stronger. Aluminium is a good conductor of heat and electricity.

Chemistry

Main article: Compounds of aluminium

Aluminium has special properties that make it different from other metals. It is lighter and its atoms are spaced farther apart.

Aluminium sticks strongly to oxygen, creating a thin layer that stops it from rusting. This helps aluminium store strong acids safely.

Aluminium can react with many other elements when heated, forming useful compounds. It also mixes well with most metals to make strong alloys.

In water, aluminium creates tiny particles that help clean the water by gathering dirt and making it sink.

Aluminium forms many different compounds with elements like fluorine and chlorine. These are used in many industries.

Aluminium also makes a hard material called alumina, which is used in sandpaper, ceramics, and other tough products.

Natural occurrence

Aluminium is found in space and on Earth. In the Solar System, it is the twelfth most common element. It is created when carbon fuses in big stars.

On Earth, aluminium is common in the Earth's crust, where it is the most abundant metal. It is usually found combined with other elements, like in minerals such as beryl and turquoise. Pure aluminium metal is very rare.

Most of the aluminium we use comes from an ore called bauxite, which is found in places like Australia, China, Guinea, and India.

History

Main article: History of aluminium

The history of aluminium began with the use of alum. People first wrote about alum a long time ago. They used it to color fabrics and protect wood from fire. After the Crusades, alum became important for making clothes in Europe.

Later, scientists learned more about alum. In 1824, a scientist made a tiny piece of aluminium metal. It was very hard to make, so aluminium was more expensive than gold for many years.

In 1856, a new way to make aluminium was found. In 1886, two engineers made an even better method called the Hall-Héroult process, which we still use today. As it became easier to make, aluminium became cheaper and was used in many things like jewelry and eyeglasses. During the world wars, aluminium was important for making airplanes.

Aluminium production grew fast in the 1900s. It was used in homes, buildings, and even in space satellites. Today, aluminium is one of the most used metals in the world.

Etymology

The words aluminium and aluminum come from an old term called alumine. This word refers to a natural material called alumina, which is the main oxide form of the metal aluminium. The term alumine came from French, and before that, from the Latin word alumen, which described a type of mineral called alum. The Latin word alumen traces back to an ancient root meaning "bitter" or "beer".

Naming and spelling history

British chemist Humphry Davy first suggested the name alumium for the metal in 1808. In 1812, Davy used the spelling aluminum in his book. Over time, aluminium became more common in many places, while aluminum became the standard in the United States and Canada. Today, both spellings are used, depending on the region.

Production and refinement

See also: List of countries by primary aluminium production

Making aluminium starts with digging up a rock called bauxite from the ground. The bauxite is cleaned and changed using the Bayer process into a substance called alumina. Then, the alumina is turned into aluminium using the Hall–Héroult process.

Creating aluminium uses a lot of energy, so factories are often built where electricity is cheap and easy to get. Making one kilogram of aluminium needs a lot of energy. As of 2024, the biggest makers of aluminium were China, India, Russia, Canada, and the United Arab Emirates.

Bayer process

Main article: Bayer process

See also: List of countries by bauxite production

The Bayer process changes bauxite into alumina. Bauxite is mixed and ground into a fine powder. This powder is then mixed with a hot liquid and treated in a special machine.

Hall–Héroult process

See also: List of countries by aluminium oxide production

The Hall–Héroult process turns alumina into aluminium. This process uses a special mix of melted materials and electricity to create aluminium. The soft metal is taken out and shaped into big blocks.

Recycling

Reusing aluminium from old items, like cans, saves energy. Melting old aluminium needs much less energy than making it from scratch. Even with some loss during recycling, it is a helpful way to get more aluminium.

Applications

Aluminium is a very useful metal. People make a lot of it because it is light, strong, and doesn’t rust easily.

We use aluminium to make cars, airplanes, trucks, trains, boats, bicycles, and spacecraft. It is also used for cans and foils. In buildings, it helps make windows and doors. It is good for electricity because it carries current well. Many home items like pots, pans, and furniture are made from aluminium because it is easy to shape and lasts a long time.

Aluminium is used in different chemical forms too. For example, aluminium oxide is very hard and is used for scrubbing things. It helps in making certain lights work. Aluminium sulfate is used to clean water and make paper. Other aluminium compounds are used in medicines and making glass.

Biology

Aluminium is very common in the Earth's crust, but it does not help living things grow or stay healthy. In most natural water, aluminium settles out and is not available for plants or animals to use.

Most of the aluminium we eat or drink passes through our bodies and comes out in our waste. However, people with kidney problems might be more affected by aluminium. Very high amounts of aluminium taken over a long time can cause health issues.

Some people can be sensitive to aluminium and may feel bad when they touch things that contain it. Workers who handle powdered aluminium or welding fumes can have breathing problems. Food, water, and some medicines are the main ways people come into contact with aluminium. If someone accidentally takes a large amount of aluminium, a special medicine can help remove it from the body.

Environmental effects

High levels of aluminium are found near places where it is mined. Small amounts can also enter the environment from coal-fired power plants or incinerators. Aluminium in the air is usually washed away by rain or settles down, but tiny particles can stay in the air for a long time.

When water is acidic, aluminium can harm animals that breathe through their gills, like fish. It can stick to their gills and cause problems. In plants, aluminium can also cause trouble, especially in acidic soil, by harming their roots. Some plants, like wheat, have found ways to protect themselves from aluminium.

Making aluminium also has environmental challenges. One big issue is the release of gases that warm the planet. These gases come from the electricity used in factories and from byproducts of processing.