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, yet 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 into shapes 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 around us, 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. This makes it easy to study using special tools. 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 easily lose three of these electrons when it reacts with other elements. This makes aluminium very useful in many chemical processes. Aluminium is a soft metal with a low melting point because it has only a few electrons that help hold its atoms together.

Bulk

Aluminium looks silvery-white to dull gray, depending on how its surface looks. 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 and other places where weight matters. Pure aluminium is soft, so it is often mixed with other metals to make it stronger. Aluminium is also a great conductor of heat and electricity, and it can even act as a superconductor under very cold conditions.

Chemistry

Main article: Compounds of aluminium

Aluminium has special properties that make it different from other metals. It has fewer electrons available for bonding, which gives it a lighter weight and longer distances between atoms.

Aluminium also has a strong pull toward oxygen, forming a thin layer of oxide that protects it from rusting. This makes aluminium useful for storing strong acids.

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

In water, aluminium forms tiny particles that can help clear the water by gathering dirt and making it settle.

Aluminium forms many different compounds, including ones with fluorine, chlorine, and other elements. These compounds are used in many industrial processes.

Aluminium also forms a hard, durable oxide called alumina, which is used in sandpaper, ceramics, and other tough materials.

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 that later explode.

On Earth, aluminium makes up about 1.59% of the planet's mass. It is very 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 feldspars, beryl, and turquoise. Pure aluminium metal is very rare and is mostly found in special places like inside some volcanoes.

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. The first written record of alum was made by a Greek historian in the 5th century BCE. People used alum for dyeing fabrics and to protect wood from fire. After the Crusades, alum became important in Europe's fabric industry and was traded from the eastern Mediterranean.

Later, scientists began to understand what alum was made of. In 1824, a Danish scientist successfully created a small piece of aluminium metal. German scientists later repeated the experiment and made more aluminium. Because it was hard to make, aluminium was very expensive and rarer than gold for many years.

In 1856, a French chemist found a new way to make aluminium that was easier and cheaper. By 1886, two engineers developed a better method called the Hall-Héroult process, which is still used today. As it became easier to make, aluminium became cheaper and was used in many everyday items like jewelry, eyeglasses, and foil. During the world wars, aluminium was important for making airplanes.

Aluminium production grew quickly during the 20th century. By the mid-20th century, it was used in homes, buildings, and even in space satellites. Today, aluminium is one of the most widely 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 was taken 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, based on the word alum. However, other scientists thought the metal should be named after its oxide, alumina, leading to the name aluminium.

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 begins with digging up a rock called bauxite from the earth. 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 as much energy as burning 7 kilograms of oil, which is more than making steel or plastic. As of 2024, the biggest makers of aluminium were China, India, Russia, Canada, and the United Arab Emirates, with China making more than half of all aluminium in the world.

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. This process dissolves the part of bauxite that makes aluminium while leaving other materials behind.

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 collects at the bottom and is taken out and shaped into big blocks for more work.

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. In 2016, people made about 58.8 million metric tons of it, which is more than any metal except iron.

People use aluminium in many ways because it is light, strong, and doesn’t rust easily. It is used to make cars, airplanes, trucks, trains, boats, bicycles, and even spacecraft. It is also used for packages like cans and foils. In buildings, it helps make windows, doors, and other parts. It is good for electricity because it carries current well and is not too expensive. 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 also used in many different chemical forms. For example, aluminium oxide is very hard and is used for scrubbing things. It helps in making certain lights work and can help speed up chemical reactions. Aluminium sulfate is used to clean water and make paper. Other aluminium compounds are used in medicines, making glass, and even in vaccines to help them work better.

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 use by plants or animals.

There is not strong proof that everyday exposure to aluminium hurts healthy adults. 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, such as problems with blood or bones.

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 close to places where it is mined. Small amounts can also be released into 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.