Atomic Properties of Bi
- Atomic Number of Bi
- 83
- Atomic Mass of Bi
- 208.9800 u
- Electron Configuration
- [Xe] 4f14 5d10 6s2 6p3
- Electronegativity
- 2.02
- Block
- p-block
- Group
- 15
- Period
- 6
Bismuth crystals sold as rainbow specimens do not reveal a rainbow-colored bulk metal. Fresh bismuth is silvery-white with a pink tinge. A thin oxide film forms as the crystal cools, and light reflected from the film's top and bottom surfaces interferes. Different film thicknesses produce shifting colors. The stepped hopper shape grows when edges advance faster than the centers of crystal faces. Color and geometry record surface oxidation and growth kinetics.
For centuries, bismuth was confused with lead and tin. Claude François Geoffroy demonstrated in 1753 that it was distinct. Today its relatively low toxicity compared with lead supports lead-free solders, low-melting safety alloys, pigments, cosmetics, and pharmaceuticals. “Lower toxicity” is not “harmless”; the compound, dose, impurities, and exposure still matter. Bismuth subsalicylate, for example, is a specific medicine with specific contraindications, not evidence that elemental bismuth treats illness.
Bismuth-209 makes up essentially all natural bismuth. It was considered the heaviest stable nuclide until researchers directly observed its alpha decay in 2003. Its half-life is about 2 times 10^19 years, over a billion times the age of the universe. For ordinary material handling it behaves as effectively stable, while nuclear physics correctly calls it radioactive.
Bismuth also expands on freezing, is strongly diamagnetic, and conducts heat poorly for a metal. Short-lived bismuth-213 is studied and used in targeted alpha-therapy systems.
This Tinkerer makes classification depend on scale. A color belongs to nanometer-thick oxide, safety is comparative, and stability changes meaning between a human lifetime and a nuclear clock.