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Bismuth

physical science Maturity 7-9 Next article →

Bismuth is a unique chemical element with the symbol Bi and the atomic number 83.

Bismuth symbol
Bismuth symbol

It is classified as a post-transition metal and belongs to a group of elements called pnictogens. This group also includes arsenic and antimony. Bismuth is highly valued because it possesses unusual physical properties that are rare among metals. It is also notable for having a much lower toxicity level than its neighbors on the periodic table. This makes it a safer alternative for many industrial and medical applications.

BrokenBismuthIngot
BrokenBismuthIngot

The physical behavior of bismuth is quite remarkable. It is a brittle metal that appears silvery-white when it is first produced. However, the surface quickly undergoes oxidation, which often creates a rosy tint. If the metal is heated, further oxidation occurs. This creates a thin layer on the surface that causes thin-film interference. This phenomenon results in a vivid, iridescent appearance with a rainbow of colors.

Wismut Kristall und 1cm3 Wuerfel
Wismut Kristall und 1cm3 Wuerfel

Bismuth also possesses extreme physical traits. It is the most diamagnetic element known, meaning it is repelled by magnetic fields. Additionally, it is one of the least thermally conductive metals. This means it does not transfer heat as easily as most other metals.

One of the most distinctive processes involving bismuth is how it changes state. Most substances shrink as they cool and solidify. Bismuth does the opposite. It expands by 3.32% during solidification. This expansion happens because the liquid phase is denser than the solid phase. This property is shared by only a few other substances, such as water and silicon.

Bi phase diagram
Bi phase diagram

This expansion was historically useful for casting printing type. The metal would expand to fill every corner of a mold perfectly. Bismuth crystals also grow in a unique way. They often form "hopper crystals" with a spiral, stair-stepped structure. This happens because the edges of the crystal grow faster than the interior edges.

Bismuth has been recognized since ancient times, so no single person is credited with its discovery. In the past, it was frequently confused with lead or tin due to its appearance. The name "bismuth" is of uncertain origin. It may come from 16th-century German words meaning "white mass."

Processing of bismuth. Etching. Wellcome V0023568
Processing of bismuth. Etching. Wellcome V0023568

In 1546, Georgius Agricola identified it as a distinct metal from tin and lead. Later, scientific progress helped clarify its identity. Johann Heinrich Pott began this work in 1738. Carl Wilhelm Scheele and Torbern Olof Bergman also helped distinguish bismuth from lead. Finally, in 1753, Claude François Geoffroy proved that bismuth was a separate element from both lead and tin.

Today, bismuth is a vital part of global industry. A large portion of its use is driven by environmental safety. Because bismuth is much less toxic than lead, it is used to create safer alloys. About one third of global bismuth production is now dedicated to replacing lead in various products.

Bismuthvanadat
Bismuthvanadat

Bismuth compounds also make up about half of the global production. These are used in pigments, cosmetics, and certain pharmaceuticals. For example, bismuth subsalicylate is a common medicine used to treat diarrhea.

Bismite
Bismite

The metal is also used in specialized medical treatments. Scientists use bismuth-213 in targeted alpha therapy to help treat certain types of cancer.

Most bismuth is not obtained through direct mining of the element itself. Instead, it is produced as a byproduct during the refining of other metals. It is often found within the ores of copper, lead, tin, molybdenum, and tungsten. One common method to separate it is the Kroll-Betterton process. Another method is the electrolytic Betts process. To reach high purity, the metal may be reacted with chlorine gas. This converts impurities into chlorides while leaving the bismuth unchanged. In 2016, the world produced 10,200 tonnes of bismuth through mining and 17,100 tonnes through refining.

For a long time, scientists believed bismuth was the heaviest stable element. They thought its nucleus would never decay. However, research in 2003 at the Institut d'astrophysique spatiale in France changed this understanding. Researchers discovered that the only primordial isotope, bismuth-209, is actually slightly radioactive. It undergoes alpha decay, which is a process where the nucleus emits an alpha particle.

Bismuth(III) oxide 2
Bismuth(III) oxide 2

Even though it is radioactive, its half-life is incredibly long. It is roughly a billion times longer than the estimated age of the universe. Because it decays so slowly, it is still treated as a stable element for almost all industrial and medical uses.

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🖼️ Images & Media (10)
File:Bismuth symbol.svg
Bismuth symbol.svg
File:Wismut Kristall und 1cm3 Wuerfel.jpg
Wismut Kristall und 1cm3 Wuerfel.jpg
File:Bi phase diagram.png
Bi phase diagram.png
File:Bismuth(III)_oxide_2.jpg
Bismuth(III)_oxide_2.jpg
File:MatlockiteStructure.png
MatlockiteStructure.png
File:Bismite.jpg
Bismite.jpg
File:BrokenBismuthIngot.jpg
BrokenBismuthIngot.jpg
File:BiPrice.png
BiPrice.png
File:Processing of bismuth. Etching. Wellcome V0023568.jpg
Processing of bismuth. Etching. Wellcome...
File:Bismuthvanadat.jpg
Bismuthvanadat.jpg
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