BISMUTH

Name: Bismuth (supposedly from the German or High German “Weissmasse” or “Weissmuth,” “white mass”)

Symbol: Bi

Group: 15

Period: 6

Block: p

Category: Post-transition metals

Atomic number: 83

Atomic mass: 208.9804 u

Electrons per shell: 2, 8, 18, 32, 18, 5

Electronegativity: 2.02

Density: 9.78 g/cc

Melting point: 271.3°C

Boiling point: 1569°C

Thermal conductivity: 8 W (m·K)

Electrical conductivity: 770,000 S/m

Magnetic order: Diamagnetic

Ordinary state: Solid

Oxidation States: +3

Mohs Hardness: 2.25

Vickers Hardness: No data

Brinell Hardness: 94.2 MPa

Most stable isotopes: Bi-209 (100% - monoisotopic element)

Discoverer: Claude François Geoffroy, French (1735)

In reality, Bismuth has been used since long before 1735; Claude Geoffroy's merit was demonstrating that it was a unique element, and not a “form” or “compound” of Lead, Tin, or Antimony, metals to which it bears resemblance for logical reasons (all are of the same category). This is so true that the very name of the metal is of German origin and alludes to its color, “white mass”, or Weissmasse, Weissmuth, Latinized Bisimutum or Bismutum, from which we get the Spanish name, “Bismuto”.

It is chemically noble enough to appear native in the Earth's crust, and its chemical inertness is such that, in a way, it behaves like a semi-precious metal (similar to Copper or Lead).

It has the heaviest metastable (or stable, if we consider the time it takes to disintegrate via alpha decay) atom in the entire Periodic Table. Thorium, Uranium, Neptunium, and Plutonium are even heavier, but their nuclei are eminently radioactive. Bismuth is as unstable as its neighbors, with the difference that in its case, “activity” has been found. In 2003, a French team detected decays via the alpha particle emission pathway in Bismuth samples, with the following reaction:

Bi-209 >> Tl-205

This process is more than a trillion times slower than the estimated age of the Universe, so for all practical purposes, it can be considered stable.

Bismuth appears in both Oxide minerals like Bismite (Bi₂O₃) and Bismuthinite (Bi₂S₃), a Sulfide, but it classifies as chalcophile (like most metals in its category, except Aluminum and, depending on the context, Tin).

For a long time, I tried to get a craftsman to forge me a ring or at least a pendant of Pewter with Bismuth content, but none dared to take on the project.

Bismuth (Bi), chemical element with atomic number 83, is a post-transition metal of group 15 (pnictogens) with a density of 9.78 g/cm³ and an abundance of ~0.008 ppm in the Earth's crust, making it rarer than lead (Pb) or tin (Sn). Although known since antiquity, its recognition as a distinct chemical element is attributed to the French chemist Claude Geoffroy the Younger in 1753, who demonstrated that it was not a form of lead, tin, or antimony (Sb), metals with which it shares similarities due to its membership in the p-block. The name "bismuth" comes from the German Weissmuth or Weissmasse ("white mass"), Latinized as bismutum, alluding to its whitish-gray color with metallic hues. Its discovery marked a milestone in 18th-century chemistry, clarifying its identity against similar metals.

The use of bismuth dates back to ancient civilizations, where it was confused with lead or tin due to its appearance and properties, such as its malleability and moderate melting point (271.4 °C). In the Middle Ages, alchemists used it in alloys and cosmetics, though without understanding its elemental nature. Geoffroy, working in Paris, isolated pure bismuth and described its properties, publishing his findings in 1753, which consolidated it as a unique element. Its chemical inertness, which allows its existence in native form in the Earth's crust, makes it similar to semi-precious metals like copper (Cu) or lead, classifying it as a chalcophile metal due to its affinity with sulfur, as observed in minerals like bismuthinite (Bi₂S₃) and bismite (Bi₂O₃).

Bismuth is notable for its relative nuclear stability. Its main isotope, Bi-209, is considered practically stable, although in 2003 a French team detected its alpha disintegration (Bi-209 → Tl-205 + α) with a half-life of 1.9 × 10¹⁹ years, more than a trillion times the age of the universe (13.8 × 10⁹ years). This makes it the heaviest metastable element, unlike radioactive thorium (Th), uranium (U), neptunium (Np), and plutonium (Pu). This stability, along with its low toxicity (compared to other heavy metals like lead or thallium, Tl), has allowed its use in modern applications, although its scarcity (8,000 tons annually in 2025) and cost (10–20 USD/kg) limit its popularity. Historically, bismuth was used in alloys like pewter (Sn-Pb-Bi), but its moderate reactivity and brittleness have hindered its use in artisan jewelry, such as rings or pendants, due to the reluctance of craftsmen to work with an unconventional metal.

Bismuth (Bi), chemical element with atomic number 83, is a post-transition metal of group 15 with a density of 9.78 g/cm³ and an abundance of 0.008 ppm in the Earth's crust. Known for its low toxicity and chemical stability, bismuth exhibits remarkable corrosion resistance, classifying it as a semi-noble metal, with a standard electrode potential (+0.317 V for Bi³⁺/Bi) higher than copper (Cu, +0.34 V) but lower than noble metals like gold (Au). Its moderate melting point (271.4 °C) and malleability allow its use in traditional casting and soldering processes, although its scarcity (8,000 tons annually in 2025) and cost (~10–20 USD/kg) limit its application. Its corrosion resistance makes it attractive for specific uses, such as alloys and jewelry.

Bismuth is highly resistant in common environments. In dry and humid air, it forms a thin layer of bismuth oxide (Bi₂O₃) which acts as a passivating barrier, protecting the metal from further oxidation. It is stable in fresh and salt water, showing minimal solubility and corrosion resistance in these media. Bismuth resists reducing acids, such as hydrochloric acid (HCl) and dilute sulfuric acid (H₂SO₄), at any concentration, forming poorly soluble compounds that retard chemical attack. However, hydrofluoric acid (HF) attacks it due to its ability to form fluorinated complexes. It is also resistant to bases and alkalis, such as sodium hydroxide (NaOH), even in concentrated solutions at room temperature. Under high-temperature conditions, its reactivity increases, especially with halogens (fluorine, F₂; chlorine, Cl₂; bromine, Br₂), forming halides such as bismuth chloride (BiCl₃).

In alloys, bismuth improves corrosion resistance and fluidity, being used in bronzes (Cu-Sn-Bi) and low-melting-point alloys, such as Wood's metal (Bi-Pb-Sn-Cd), which take advantage of its low melting temperature. In pewter or costume jewelry, it is incorporated into alloys (Sn-Pb-Bi) to add durability and a shiny finish, although its brittleness limits its use in pure pieces. Bismuth's chemical stability, along with its low toxicity compared to heavy metals like lead (Pb) or thallium (Tl), makes it suitable for applications where safety is a priority. However, its reactivity under hot conditions and with halogens requires precautions in specific industrial environments.

Bismuth (Bi), chemical element with atomic number 83, is a post-transition metal of group 15 with a density of 9.78 g/cm³ and an abundance of 0.008 ppm in the Earth's crust. Known for its low toxicity compared to other heavy metals like lead (Pb) or thallium (Tl), and its corrosion resistance, bismuth is primarily used as an alloying agent in applications that take advantage of its low melting point (271.4 °C) and chemical compatibility. Although its brittleness (Mohs hardness ~2.25) limits its use as a pure metal in metallurgy, its global production (8,000 tons annually in 2025) and moderate cost (~10–20 USD/kg) make it valuable in industrial, military, and decorative sectors, often as a lead substitute due to environmental and health concerns.

In alloys, bismuth is a key component in low-melting-point eutectic alloys, such as Wood's metal (50% Bi, 25% Pb, 12.5% Sn, 12.5% Cd) or Rose's metal (50% Bi, 28% Pb, 22% Sn), used in solders, fuses, and electrical contacts. These alloys, with melting points as low as 70–95 °C, are ideal for applications requiring fluidity at low temperatures, replacing lead in solders (e.g., 60% Bi-40% Sn) to reduce toxic risks. Bismuth is compatible with metals like cadmium (Cd), tin (Sn), indium (In), lead, thallium, mercury (Hg), and gallium (Ga), but its affinity with zinc (Zn) and aluminum (Al) is lower, resulting in brittle alloys. In pewter (Sn-Pb-Bi), small amounts of bismuth (1–2%) improve shine and corrosion resistance, although antimony (Sb) has replaced it in applications requiring greater toughness. In bronzes (Cu-Sn-Bi), bismuth (0.5–6%) provides self-lubricating properties and corrosion resistance, similar to lead bronzes, but without toxicity. Its insolubility in copper requires its addition along with tin to facilitate machining and chip formation.

In military applications, bismuth is used as a lead alternative in non-toxic ammunition, combined in alloys (e.g., Bi-Sn) for bullets and pellets. Pure bismuth is too brittle and would fragment upon firing, but alloys offer sufficient density (~9–10 g/cm³) to maintain kinetic energy. In radiological shielding, bismuth is an alternative to lead and tungsten carbide (WC) in protection against ionizing radiation, such as in X-ray rooms or nuclear containers, due to its high atomic weight (Z=83) and lower toxicity. In jewelry and decoration, bismuth is used in alloys for ornamental pieces, toys, and costume jewelry, leveraging its metallic luster and safety, although its use is rare due to brittleness. Historically, bismuth-manganese (Bi-Mn) alloys were used to make permanent magnets, but have been replaced by more efficient materials.

Bismuth does not wet glass (it does not react with SiO₂) and can be melted without risks, as its vapors are not toxic, unlike lead or mercury. This property, along with its chemical stability, makes it suitable for applications where safety is a priority. In medicine, compounds like bismuth subsalicylate (BiC₆H₅O₇) are used in medications to treat gastric conditions, taking advantage of its low toxicity. Bismuth's versatility, driven by its chemical compatibility and relative safety, positions it as a viable lead substitute in the context of strict environmental regulations, such as RoHS, which limits the use of toxic metals in electronics.

Bismuth (Bi), chemical element with atomic number 83, is a post-transition metal of group 15 with a density of 9.78 g/cm³ and an abundance of 0.008 ppm in the Earth's crust. Its main isotope, Bi-209, is notable for being the heaviest element considered practically stable, although in 2003 a French team led by the Institut de Physique Nucléaire d'Orsay demonstrated that it undergoes alpha decay with an extraordinarily long half-life of approximately 1.9 × 10¹⁹ years, more than a trillion times the estimated age of the universe (13.8 × 10⁹ years). This process, which converts Bi-209 into thallium-205 (Tl-205), highlights bismuth as the heaviest metastable element, in contrast to heavier elements like thorium (Th), uranium (U), neptunium (Np), and plutonium (Pu), which are clearly radioactive.

The alpha decay of Bi-209 occurs through the emission of an alpha particle (two protons and two neutrons, equivalent to a helium nucleus, He-4), transforming into Tl-205 according to the reaction:

Bi-209 → Tl-205 + α (He-4).

This process releases energy of ~3.14 MeV, but its probability is extremely low due to the stability of the Bi-209 nucleus, attributed to its electron configuration ([Xe] 4f¹⁴ 5d¹⁰ 6s² 6p³) and the inert pair effect, which stabilizes the 6s electrons and hinders nuclear rupture. The half-life of Bi-209 is so prolonged that, for all practical purposes, it is considered stable for industrial and chemical applications, such as eutectic alloys or medicines (bismuth subsalicylate, BiC₆H₅O₇).

The discovery of this disintegration, published in Nature in 2003, marked a milestone in nuclear physics, confirming that Bi-209 is not completely stable, as previously thought. Experiments used highly sensitive detectors to capture the rare alpha emissions in pure bismuth samples, revealing its minimal radioactivity. This property does not affect its practical use, given that the radioactive activity (~0.025 disintegrations per second per kg) is insignificant compared to elements like uranium (U-238, ~12,400 disintegrations per second per kg). The alpha decay of Bi-209 underscores its uniqueness in the periodic table, positioning it as a bridge between stable and radioactive elements, and reinforces its scientific interest in studies of nuclear physics and cosmochemistry.