Bismuth is the element with symbol Bi and atomic number 83. As a post-transition metal that often occurs in the company of heavy metals like lead and tin. Despite its density, bismuth has some remarkable characteristics that distinguish it from other elements. You encounter this element in everyday life in medicines, cosmetics, and as a replacement for lead in products.
Discovery, Naming, and Isolation
Bismuth has been known since ancient times, often confused with lead and tin due to its similar appearance. The German monk Basil Valentine made the first written description of bismuth in the 15th century, although it was known and used earlier. The name “bismuth” comes from the German words “wismut” or “wissmuth,” which means “white mass.” The element was isolated and distinguished from lead and tin by the French chemist Claude François Geoffroy in 1753.
Appearance and Unusual Properties
Bismuth is a brittle metal with a silver-pink hue, known for its low thermal conductivity and high electrical resistivity compared to other metals. A thin bismuth layer acts as a semiconductor. Oxidation eventually gives bismuth an iridescent rainbow coating. The crystals take on a hopper shape, with a spiral stair-step structure. One of the most unusual properties of bismuth is its diamagnetism. It is the most strongly diamagnetic element known, which means it repels magnetic fields. Bismuth burns with a blue flame. Its oxide evolves yellow fumes.
Bismuth has a higher density as a liquid than as a solid. Like water, the element expands as it solidifies.
Element Group
Bismuth is a member of group 15 in the periodic table, which is also known as the nitrogen group. This group includes nitrogen, phosphorus, arsenic, antimony, and bismuth, and elements in this group typically have five electrons in their outermost shell.
Isotopes of Bismuth
Bismuth has one natural isotope, bismuth-209, which is stable with a very long half-life of approximately 2.1 × 1019 years, making it effectively stable for practical purposes. There are synthetic isotopes of bismuth, ranging from bismuth-195 to bismuth-215, all of which are radioactive with much shorter half-lives.
Abundance and Sources
Bismuth is relatively rare in the Earth’s crust, with an abundance of about 0.009 ppm. Although not common, the element occurs in relatively pure native form. It is abundant in the minerals bismuthinite (Bi2S3) and bismite (Bi2O3). Significant sources of bismuth include Bolivia, Peru, Japan, Mexico, and Canada. It is often a byproduct of refining lead, copper, tin, silver, and gold ores. While recycling the element is possible, it is not economically practical at present.
Purification
The purification of bismuth involves several steps. Roasting bismuth ores removes sulfur and oxidizes the bismuth. Reducing the resulting bismuth oxide with carbon yields metallic bismuth. Electrolytic refining or zone refining further purifies the metal.
Uses of Bismuth
Bismuth has a wide range of applications, including:
- Pharmaceuticals: Bismuth compounds like bismuth subsalicylate are ingredients in medications for treating indigestion, diarrhea, peptic ulcer, and other gastrointestinal disorders. Other uses include treatments for eye infections, odors from fecal matter or flatulence, and also cadmium poisoning.
- Cosmetics: Bismuth oxychloride gives cosmetics a pearlescent effect.
- Metallurgy: Bismuth is a replacement for lead in free-machining alloys and as a coolant in nuclear reactors due to its low melting point.
- Pigments: Bismuth vanadate is a non-toxic, bright yellow pigment in paints and coatings. Other compounds yield white pigments and replacements for more toxic cadmium pigments.
- Fusible Alloys: Bismuth is useful in alloys that melt at low temperatures. These alloys are key in safety devices like fire sprinklers and electric fuses.
- Semiconductors: Bismuth telluride is an important thermoelectric material used in cooling devices.
- Lead Replacement: Bismuth replaces lead in ballistics, x-ray shields, solders, and other applications that use highly toxic lead.
Additional uses include superconducting compounds, thermoelectric materials, solid electrolytes, scintillators, catalysts, lubricant greases, and crackling fireworks.
Oxidation States
The oxidation states of bismuth range from -3 to +5. Bismuth primarily exhibits the +3 oxidation state. The +5 state is less stable and less common. Bismuth’s ability to form stable compounds in the +3 state comes from its reluctance to lose more electrons, a characteristic known as the inert pair effect.
Biological Role, Health Effects, and Toxicity
Bismuth has no essential biological role in humans or other organisms. However, bismuth compounds generally have low toxicity, at least compared with other heavy metals. Ingestion of large amounts of bismuth causes kidney damage and other health issues. The biological half-life of the element in the human body is around 5 days, although it sometimes accumulates in persons taking bismuth compounds as medicine.
Bismuth poisoning sometimes occurs. Like lead, excessive bismuth forms a black deposit along the gingiva in the mouth. The ecological impact of the increasing use of bismuth remains an area of active research.
Key Bismuth Facts Table for Scientists
| Property | Value |
|---|---|
| Name | Bismuth |
| Symbol | Bi |
| Atomic Number | 83 |
| Atomic Weight | 208.9804 |
| Group | 15 (Nitrogen Group) |
| Period | 6 |
| Block | p-block |
| Electron Configuration | [Xe] 4f14 5d10 6s2 6p3 |
| Electrons per Shell | 2, 8, 18, 32, 18, 5 |
| State of Matter at Room Temp | Solid |
| Melting Point | 271.4°C |
| Boiling Point | 1564°C |
| Density | 9.807 g/cm³ |
| Heat of Fusion | 11.30 kJ/mol |
| Heat of Vaporization | 179 kJ/mol |
| Molar Heat Capacity | 25.52 J/(mol·K) |
| Oxidation States | -3, -2, -1, 0, +1, +2, +3, +4, +5 |
| Electronegativity | 2.02 (Pauling scale) |
| First Ionization Energy | 703 kJ/mol |
| Second Ionization Energy | 1610 kJ/mol |
| Third Ionization Energy | 2466 kJ/mol |
| Atomic Radius | 156 pm |
| Covalent Radius | 148 pm |
| Van der Waals Radius | 207 pm |
| Crystal Structure | Rhombohedral |
| Thermal Conductivity | 7.97 W/(m·K) |
| Electrical Resistivity | 1.29 µΩ·m |
| Magnetic Ordering | Diamagnetic |
| Young’s Modulus | 32 GPa |
| Shear Modulus | 12 GPa |
| Mohs Hardness | 2.25 |
Interesting Bismuth Facts
- Colorful Crystals: Bismuth crystals have a beautiful iridescent oxide layer, which produces a rainbow of colors due to thin-film interference. Because of the low toxicity and melting point of the metal, many people grow bismuth crystals themselves.
- Heaviest Stable Isotope: Bismuth-209 was the heaviest known stable isotope until recent studies showed it has an extremely long half-life, making it effectively stable.
- Low Toxicity: Unlike many other heavy metals, bismuth compounds are relatively non-toxic, making them useful in medicine and cosmetics.
- Pepto-Bismol: One of the most common over-the-counter medications, Pepto-Bismol, contains bismuth subsalicylate, highlighting its role in treating gastrointestinal issues. Extracting bismuth from the preparation is a simple science project.
- Low Melting Point Alloys: Bismuth is a key component in many low melting point alloys, including fuses, other safety devices, and fire detection systems.
References
- Hoffman, C.; Meyer, J.; et al. (1993). “Semimetal-to-semiconductor transition in bismuth thin films”. Phys. Rev. B. 48 (15): 11431–11434. doi:10.1103/PhysRevB.48.11431
- Norman, Nicholas C. (1998). Chemistry of Arsenic, Antimony, and Bismuth. Springer. ISBN 978-0-7514-0389-3.
- Ojebuoboh, Funsho K. (1992). “Bismuth—Production, properties, and applications”. JOM. 44 (4): 46–49. doi:10.1007/BF03222821
- Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. ISBN 0-8493-0464-4.
- Weeks, Mary Elvira (1932). “The discovery of the elements. II. Elements known to the alchemists”. Journal of Chemical Education. 9 (1): 11. doi:10.1021/ed009p11