Aluminium (Al)

Aluminium is a chemical element with the atomic number 13 in the periodic table of elements. It’s the most plentiful metal found in the Earth’s crust. Being a member of the boron family of periodic table elements, this strong and light-weight metal has three valence electrons that help aluminium make numerous compounds with the other chemical elements.

Physical and Chemical Properties of Aluminium

Atomic number13
Atomic weight26.981539 g.mol-1
ColorSilvery-grey metallic with a bluish tint
Physical stateSolid
Melting point933.52°C, 933.473 K
Boiling point2720°C, 2792 K
Van der Waals radius0.143 nm
Ionic radius0.54 nm (+3)
Artificial isotopes16
Electronic shell[Ne] 3s2 3p1
The energy of the first ionization577.4 kJ.mol-1
The energy of the second ionization1816.1 kJ.mol-1
The energy of the third ionization2744.1 kJ.mol-1
DiscovererHans Christian Oersted
Crystal StructureCubic: Face centered
Covalent Radius1.18 Å
Atomic Radius1.82 Å
Atomic Volume10.0 cm³/mol
Name OriginLatin: alumen, aluminis, (alum)
Oxidation States3
UsesUsed for many purposes from airplanes to beverage cans. Too soft in its pure form so less than 1% of silicon or iron is added, which hardens and strengthens it.
DescriptionAmorphous form is brown powder; crystalline form has grey metallic appearance. Seventh most abundant element in the universe. Second most plentiful element in the earth’s crust.

With the periodic table symbol Al, atomic number 13, atomic mass of 26.981539  g.mol -1, and electronic configuration [Ne] 3s² 3p¹, actinium is ductile and reaches its boiling point at 2519°C, 4566°F, 2792 K, while the melting point is achieved at 660.323°C, 1220.581°F, 933.473 K. 

This member of the boron family of elements in the periodic table has an electronegativity of 1.6 according to Pauling, whereas the atomic radius according to van der Waals is 143 pm. 

Despite being light and soft in its pure form, aluminium is a strong metal that becomes even stronger when alloyed with another metal. Mainly found in bauxite, this silvery-grey element of the periodic table is easily bent and makes for an excellent heat and electricity conductor. It’s a non-absorbing, non-magnetic, corrosion-resistant substance with a low density of 2.7 g/cm -3.

How Was Aluminium Discovered?

In 1824, the Danish physicist Hans Christian Oersted (August 14, 1777, Rudkøbing, Denmark – March 9, 1851, Copenhagen, Denmark) first managed to isolate aluminium from the aluminium chloride compound. With the help of a potassiummercury amalgam, he successfully produced a tin-resembling lump that later became the most used and the most versatile metal on Earth. 

In 1827, the German chemist Friedrich Wöhler (July 31, 1800, Eschersheim, Frankfurt, Germany – September 23, 1882, Göttingen, Germany) produced aluminium in pure form for the first time. The extracted element was a powdery substance that got its familiar silvery and shiny form by undergoing a melting process. 

The American inventor and chemist Charles Martin Hall (December 6, 1863 – December 27, 1914) managed to invent an inexpensive method of aluminium production. This eventually lead to cheap production and wide application of this metal.  

How Did Aluminium Get Its Name?

The name of aluminium comes from the Latin word alumen (aluminium potassium sulfate – KAl(SO4)2∙12H2O) denoting ‘bitter salt’. British chemist Sir Humphry Davy (17 December 1778 – 29 May 1829) had initially labeled this chemical element as ‘aluminium’, which is the preferred name in the USA. 

However, the Europeans have decided to go with “aluminium” as the name for the 13th  number on the periodic table of elements, while the American Chemical Society kept the name “aluminium”.

Where Can You Find Aluminium?

Rarely found in its pure form in nature, aluminium is mainly extracted from bauxite and cryolite ores. There’s also 8.1% of this substance in the Earth’s crust, which makes aluminium the most abundant metal in nature, as well as the third most abundant element (after oxygen and silicon).

Due to its chemical properties, aluminium has many applications. This soft metal can be used in various industries, such as medicine, the aerospace and automotive industries, construction, etc. Aluminium food cans, beverage cans, cooking utensils, transmission lines, and aluminium foil are the most used (Al) products in everyday life. 

Bauxite (Al2H2O4)   

This aluminium-rich ore labeled as bauxite was first discovered near the village of Les Baux, hence its name. Nowadays, bauxite is mainly mined in Guinea, Australia, and China. This rock with a reddish-clay hue is the main source of aluminium, extracted by the use of the Bayer process. Composed of alumina, silica, titanium dioxide, and iron oxides, bauxite is refined to aluminium by electrolysis and the Hall–Héroult process.

Cryolite (Na3AlF6)

Cryolite is a halide mineral whose color varies from white to colorless. It’s used to decrease the melting point of aluminium, while increasing its conductivity. In this way, cryolite supports a more inexpensive aluminium production. The largest cryolite mining sites are located in Ivigtut, Greenland, as well as in Colorado, USA, and Spain. In addition, the United States was the world’s largest aluminium producer for many years. 

Aluminum Foil

Nowadays, there’s almost no household that doesn’t use aluminium foil. Made of 98.5% pure aluminium, the wide application of this foil is evident in food packaging (chocolates, thermo-isolation of food), cosmetics, medicine products, etc. 

Apart from the home use of aluminium foil, it’s also employed in construction, mainly as a thermal insulator, or for the isolation of electric cables, due to its barrier-providing properties. 

Aluminium in the Building and Construction Industries

The classification as a non-combustible material also makes aluminium one of the safest building and construction materials. Due to its water and corrosion resistance, this lightweight metal has a large degree of bending which makes it one of the most ideal materials for the building and construction industries. 

The aforementioned physical properties make this member of the boron family of elements suitable to be widely applied in the production of windows, staircases, doors, and roofs, alone or as a part of aluminium alloys. 

The Aluminium Association is the main industry group trading aluminium, located in Arlington, Virginia, United States. Formerly based in Washington D.C., this association was managing this metal as a strategic substance during World War II. Its first assembly was held in New York City in 1935. Nowadays, the aluminium industry is one of the most developed and profitable industrial and trading branches. 

Aluminum in the Automotive Industry and Aerospace Technology

Having a wide application in transportation, aluminium provides broad opportunities for the establishment of complex transport networks that shape the world as we know it. Being both strong and light-weight, in addition to being easily bendable, the aluminium metal is ideal for durable and safe construction of water, air, land, and even space vehicles. 

Aluminum in Food

Traces of aluminium can be naturally found in some foods, such as some tea herbs, cake mixes, self-rising flour, mineral water, etc. Some processed foods contain aluminium enriched additives in the form of raising agents, coloring agents, or stabilizers. These additives can be found in some processed cheeses, salt, etc.

As an illustration, the following is a list of foods with their average levels of aluminium concentration:

  • Mineral water – 2 mg/L
  • Carbonated drinks in cans – 0.66 mg/L
  • Carbonated drinks in glass bottles – 0.24 mg/L
  • Wine – 2 mg/L
  • Tea – 2.1 ± 0.1 mg/L
  • Potato – 5.88 mg/Kg
  • Spinach – 27.47 ± 38.47 mg/Kg
  • Banana – 32.80 ± 33.05 mg/Kg

Aluminium Recycling

Items made of aluminium are the most recyclable waste. By recycling only one aluminium can, we can save as much energy as to fully charge an iPod. 

How Dangerous Is Aluminium?

Since aluminium has a broad application in our everyday life, we are often exposed to its potentially harmful effects by using aluminium-made products or consuming aluminium-containing foods. This metal is present in some foods enriched with aluminium via contaminated irrigation waters or soil, where it can also be found naturally. Furthermore, we tend to use kitchen cutlery and utensils in which aluminium is also present. 

Many cosmetic products contain aluminium. In particular, antiperspirant deodorants are often made with aluminium chlorohydrate or aluminium zirconium tetrachlorohydrex gly that prevent excessive perspiration by blocking the pores on the skin. This is a potential health hazard that can easily result in some more serious health diseases, such as Alzheimer’s disease. 

Aluminum Toxicity

Aluminium toxicity occurs when the concentration of aluminium in the body is far above the normal level. We can be exposed to aluminium by consuming food and liquids that contain aluminium, or by inhaling aluminium dust from aluminium mining sites or hazardous wastes. 

The person affected by aluminium toxicity typically feels confusion, weakness of the muscles, experiences seizures, or has difficulty speaking. Very often, anemia, as well as brain and lung diseases occur as a complication due to the toxic exposure to aluminium. 

Environmental Effects of Aluminium

Acidic precipitation is the main pollution agent of the waters and soil that results in high aluminium concentration in the ecosystems. Plants absorb the acidic, toxic metal from the soil. In this way, they become a harmful link in the food chain of both humans and animals.  

Aluminum Isotopes

This chemical element has 22 isotopes and 4 isomers. Among them, only aluminium-26 (26Al isotope) and aluminium-27 (27Al isotope) are naturally abundant. In addition, aluminium-27 (27Al isotope) is the only stable isotope of aluminium, while aluminium-26 (26Al isotope) radiates with β-radiation. 

List of Aluminum Compounds

  1. Aluminium ammonium sulfate (NH4)Al(SO4)2: This aluminium compound is used for purification of waters, in deodorants and antiperspirants, in the textile industry;
  2. Aluminium borate (AlBO3): Applied mainly in some industrial branches, such as ceramic manufacture and water purification and treatment;
  3. Aluminium borohydride (H12AlB3): The compound of sodium borohydride and  aluminium chloride is mainly used as spacecraft fuel and a chemical reducing agent;
  4. Aluminium chloride (AlCl₃): Applied in medicine for the treatment of excessive perspiration;
  5. Aluminium fluorosilicate (AlF3O6Si3): This aluminium compound is used as a disinfectant solution, for water treatment, and in metal casting;
  6. Aluminium hydroxide (Al(OH)3): Used as an antacid, this chemical compound is applied in medical conditions affecting the digestive system of our body; 
  7. Aluminium phosphate (AlPO4): Applied in the dental, pharmaceutical, and cosmetic industry, as well as in the production of paint and paper;
  8. Aluminium sulfate, or alum (Al2(SO4)3): This aluminium compound is used as an active ingredient in textile dyeing, water purification, paper production, as a coagulant in medicine, in the food industry, etc. 
  • Aluminium oxide (Al2O3): The compound of aluminium and oxide have a rock-forming crystalline, labeled as corundum. This crystalline occurs in two forms of precious stones – ruby (red) and sapphire (blue). 

5 Interesting Facts and Explanations

  1. When combined with other elements, such as copper or magnesium, aluminium becomes even stronger as alloy. 
  2. Bauxite is an aluminium ore, consisting of a combination of aluminium, oxygen, and other chemical elements. This compound is the main source of Al in nature. 
  3. aluminium can also be extracted from compounds such as beryl, turquoise, feldspar, cryolite, etc.
  4. Aluminium foil keeps food fresh without cooling. It also prevents contamination, moisturization, and oxygenation of the ingredients.   
  5. Metal‐grade alumina is the most exploited aluminium compound.