Bismuth

Bismuth is a beautiful metalloid with a distinctive pinkish-white tint and the remarkable property of forming rainbow-coloured, staircase-shaped crystals when it slowly solidifies. It is the heaviest stable element and the active ingredient in Pepto-Bismol stomach medicine.

  • Atomic Number8383 protons, 83 electrons
  • Atomic Mass208.98040 u83× heavier than hydrogen
  • State at Room TempSolidSolid
  • Density9.807 g/cm³
  • Melting / Boiling271.4°C / 1563.8°C
  • Discovered1753

What is Bismuth?

Bismuth has 83 protons and is the heaviest element with any stable isotope (bismuth-209). It expands slightly on solidifying (like water), making it useful in low-melting alloys for safety sprinklers. Its compounds are non-toxic and are replacing lead in many applications.

Known since the Middle Ages; confused with lead and tin. Named from the German Wismut or Weissmuth. Recognised as distinct from lead by Claude François Geoffroy in 1753.

Fact Bismuth grows into spectacular, iridescent "hopper crystals", staircase-shaped squares within squares, when slowly cooled from the melt. The rainbow colours arise from a thin oxide film of varying thickness on the crystal surface, which causes thin-film interference of light. Large, perfect bismuth crystals are grown by hobbyists as decorative art objects.

Where you find Bismuth

On Earth

By-product of lead, copper and tin smelting. China, Peru, Mexico and Bolivia are major producers.

How we use Bismuth

  • Medicine.. Bismuth subsalicylate (Pepto-Bismol) treats stomach upset, diarrhoea and indigestion. It works by coating the stomach lining and has mild antibacterial effects against H. pylori.
  • Low-melting alloys.. Bismuth alloys melt below 100°C, used in fire sprinkler fusible links that melt in a fire to release water.
  • Shotgun pellets.. Bismuth shot is replacing lead shot for waterfowl hunting, as it is non-toxic and has similar density.

How it was discovered

Known since the Middle Ages; confused with lead and tin. Named from the German Wismut or Weissmuth. Recognised as distinct from lead by Claude François Geoffroy in 1753.

Deeper dive: bismuth properties

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Moving to 84 protons on the periodic table takes us to the next element.