Bismuth · element 83
The rainbow-coloured metal that is technically radioactive yet will outlast the universe many times over
Key facts
Bismuth is the element that looks like it was designed for a science museum. Melt it, let it cool slowly, and it grows into staircase shaped crystals covered in shimmering pinks, blues, golds and purples. The colours are not paint or dye; they come from a skin of oxide so thin that light waves bouncing off its top and bottom interfere with each other.
It is also the friendly neighbour in a rough part of the table. Sitting between lead and polonium, bismuth is remarkably non-toxic, which is why it turns up in stomach medicines and is replacing lead in everything from shotgun pellets to plumbing fittings.
Where it is found
Bismuth is scarce, roughly as rare in the crust as silver. It occurs as the native metal and in the minerals bismuthinite, a sulfide, and bismite, an oxide, but deposits rich enough to mine for bismuth alone are unusual. Nearly all supply is a by-product of refining lead, copper, tin and tungsten ores.
China produces the great majority of the world's bismuth, with smaller amounts from Laos, South Korea, Japan, Bolivia and Mexico. Because it rides along with other metals, its supply depends on how much lead and tungsten are being refined rather than on demand for bismuth itself.
How it was discovered
Medieval miners in Germany knew bismuth well and used it, but they were never sure what it was. It was often confused with tin and lead, and the sixteenth century mining writer Georgius Agricola described it as a distinct metal without fully proving it. The name may come from the German weisse Masse, white mass, though the origin is uncertain.
The credit for showing that bismuth is its own element usually goes to the French chemist Claude François Geoffroy, who demonstrated in 1753 that it was different from lead in every chemical test. Long before that, printers had been adding bismuth to type metal because it lowered the melting point and, unusually, expanded as it solidified, pressing the metal into every corner of the mould.
What we use it for
Millions of people take bismuth without knowing it. Bismuth subsalicylate is the active ingredient in a well known pink liquid for upset stomachs, and bismuth compounds are part of the standard treatment for stomach ulcers caused by the bacterium Helicobacter pylori. The harmless side effect is a black tongue, caused by bismuth sulfide.
Bismuth's low melting point makes it the basis of alloys that melt in hot water. These plug fire sprinkler heads, act as safety fuses, and hold delicate parts during machining. As a lead substitute it appears in shotgun pellets for wildfowling, fishing weights, solders and brass for taps. Bismuth oxychloride gives the pearly shimmer to eyeshadow and nail varnish, bismuth vanadate is a bright yellow pigment replacing toxic lead and cadmium yellows, and bismuth telluride is the working material in the small solid state coolers used in portable fridges and to chill computer chips.
Reading the numbers
Bismuth melts at about 271 °C, one of the lowest melting points of any metal outside the alkali metals, and boils near 1560 °C. A camping stove will melt it, which is why growing bismuth crystals is a popular home experiment under adult supervision. Its density of 9.78 grams per cubic centimetre is nearly ten times that of water but noticeably less than lead's 11.34.
The electron configuration [Xe] 4f14 5d10 6s2 6p3 gives five outer electrons and puts bismuth in group 15 with nitrogen, phosphorus, arsenic and antimony. Walk down that group and you travel from a colourless gas through waxy and brittle non-metals to a shiny metal; bismuth is the metallic end of the journey. It mostly forms +3 compounds, keeping its 6s pair to itself. An electronegativity of 2.02 and first ionisation energy of 703 kJ/mol are middling. Bismuth is also the most strongly diamagnetic of all metals, and one of the few materials, along with water, that expands when it freezes.
Safety and the environment
Bismuth metal and most of its compounds are poorly absorbed by the body and are considered among the least toxic of the heavy metals. Very large doses of bismuth medicines taken over months have caused reversible confusion and problems with movement, which led to tighter limits on their use, but ordinary short courses are safe.
Environmentally, bismuth is welcome. Every gram used in shot, weights, solder or brass is a gram of lead that is not being scattered into rivers, soils and wildlife. Its radioactivity is real but meaningless: bismuth-209 decays so slowly that the amount lost since the Earth formed is undetectable.
Did you know?
- Bismuth-209 was long thought to be stable, but in 2003 physicists measured its half-life at about 20 billion billion years, more than a billion times the age of the universe.
- The rainbow colours on bismuth crystals come from a thin oxide film that makes different wavelengths of light interfere, the same effect as a soap bubble.
- Bismuth expands by about three per cent as it solidifies, one of very few substances besides water to do so.
- Bismuth is the most diamagnetic metal, meaning it pushes back against a magnet more strongly than any other.
- Taking bismuth stomach medicine can temporarily turn your tongue black, because bismuth reacts with sulfur compounds in the mouth.
- Alloys of bismuth with lead, tin and cadmium can melt below the boiling point of water, and one of them plugs fire sprinkler heads.
More in the post-transition metals
Column-mates come first, since elements in one column have outer electrons arranged in a similar way and tend to behave alike; the rest are the nearest neighbours in the family.
See all 12 post-transition metals on one page, or browse all 118 elements.
Frequently asked questions
Is bismuth radioactive?
Technically yes, but only just. Its one natural isotope, bismuth-209, has a half-life of around 20 billion billion years, so its radioactivity is far too weak to measure in everyday life or to pose any risk. For practical purposes it is treated as stable.
Is bismuth toxic?
Bismuth is one of the least toxic heavy metals and is used in medicines for the stomach. Very high doses over long periods can cause neurological problems, so bismuth medicines are meant for short term use. Handling the metal is safe.
Why does bismuth have rainbow colours?
When molten bismuth cools in air, a very thin layer of bismuth oxide forms on its surface. Light reflecting from the top and bottom of that layer interferes, and the colour you see depends on the thickness, so different faces of a crystal show different colours.
Can you grow bismuth crystals at home?
Yes, with care. Bismuth melts at about 271 °C, within reach of a camping stove or hotplate, and slow cooling in a metal container produces hopper crystals. Molten metal causes severe burns, so it should only be done by adults or with close supervision.
Read next
Guess the mystery element in six tries. A new one every day, free, no sign-up.
Written by Anthony. Updated September 2026. Numerical data from Periodic-Table-JSON (CC BY-SA), cross-checked against the Bismuth reference article. Spotted an error? Tell us.