Bismuth (Bi)
“Lead’s look-alike, yet gentle enough to put in stomach medicine — and it grows rainbow stair-step crystals that look machine-made.”
How its electrons are arranged
Computed from the aufbau principle, with known real-world exceptions applied automatically.
Characteristics
- Electron configuration [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p³ — period 6, group 15, p-block, five valence electrons; its favourite ion is Bi³⁺, echoing the nitrogen family above it.
- A rare physical quirk: like water, bismuth expands about 3% on freezing, so castings come out sharp instead of shrinking — the reason it stars in detailed moulds and fusible alloys.
- Melts at just 271 °C — low for a heavy metal — conducts heat worse than almost any other metal, and is the most strongly diamagnetic metal known.
- Bi-209 was long counted the heaviest stable nuclide; in 2003 French physicists caught it emitting an alpha particle with a half-life of 2×10¹⁹ years — over a billion times the age of the universe — so “practically stable” is the honest label.
A brittle, silvery-white metal with a faint pink blush, noticeably lighter than the lead it impersonated for centuries. Left in air, it grows a thin oxide skin whose interference colours turn lab-grown crystals into iridescent, rainbow staircases.
Where you meet it
✦ Uses
- Bismuth subsalicylate — the pink, wintergreen-flavoured stomach medicine sold worldwide as Pepto-Bismol — treats indigestion and diarrhoea; its cousin bismuth subcitrate still fights H. pylori in modern quadruple therapy.
- Lead-free solders and pewter: electronics and plumbing increasingly swap toxic lead for bismuth alloys, which melt low and shrink nothing on cooling.
- Fusible safety alloys: Wood’s metal — roughly half bismuth — melts near 70 °C, so it plugs the links of automatic fire sprinklers and thermal fuses in boilers.
- Cosmetics and colour: bismuth oxychloride gives nail polish and eye shadow their pearl-frost shine, while bismuth telluride (Bi₂Te₃) forms the heart of Peltier thermoelectric coolers in portable car fridges.
◍ Everyday examples
- The candy-pink Pepto-Bismol bottle on a pharmacy shelf is the world’s best-known bismuth product.
- Science shops sell lab-grown bismuth “rainbow crystals” — stair-step hopper pyramids no bigger than a dice — as desk ornaments.
- Any lead-free-soldered phone board or modern plumbing joint quietly carries bismuth in lead’s old job.
History & name
Miners in the Ore Mountains had smelted bismuth since the Middle Ages, but for centuries it was traded as a lazy kind of lead or tin — Agricola in 1546 even described it as a “bastard” metal. The French chemist Claude Geoffroy the Younger settled the matter in 1753, showing that bismuth’s brittleness, crystals and furnace behaviour made it an element in its own right, distinct from lead. Its name travelled from the miners’ word Wismut — often read as “white mass”, for the pale, stony ore — through Agricola’s Latin bisemutum to today’s bismuth.