Overview

Bismuth is the chemical element with atomic number 83 and the symbol Bi. It sits in group 15 of the periodic table and is classified as a post‑transition metal or pnictogen. Its standard atomic mass is close to 209. For a concise element profile see element summary and for its place on the table consult the periodic entry.

Physical and chemical characteristics

Bismuth is a dense, silvery metal that often shows a pinkish tint caused by surface oxidation. It crystallizes in a rhombohedral lattice and tends to be brittle rather than malleable. Bismuth has low thermal conductivity compared with many other metals and is weakly diamagnetic. It forms a variety of compounds, including notable alloys and semiconducting tellurides used in thermoelectric materials.

History and natural occurrence

Known to metallurgists and alchemists for centuries, bismuth was recognized as a distinct element as modern chemistry developed in the 18th century. It occurs in nature primarily as a byproduct of mining for lead, copper and tungsten and can be found in native form or in ores. Commercial bismuth typically comes from refining operations where it is separated from other heavy metals.

Uses and applications

  • Pharmaceuticals and cosmetics: certain bismuth compounds are active ingredients in digestive medicines and in some topical products.
  • Alloys and solders: bismuth enters low‑melting and fusible alloys valued for predictable melting behavior and for lead‑replacement uses in plumbing and fishing weights.
  • Thermoelectrics and semiconductors: compounds such as bismuth telluride are important for cooling and power‑generation devices.
  • Pigments and metallurgy: bismuth oxide and oxychloride appear in pigments and specialty ceramic uses.

Isotopes and radioactivity

Natural bismuth occurs essentially as a single nuclide, bismuth‑209, long regarded as stable. Sensitive measurements established that it undergoes an extremely slow radioactive decay, but its activity is so low that bismuth is treated as effectively nonradioactive in everyday use. For atomic mass and isotope details consult atomic data and isotope information.

Notable facts and distinctions

Bismuth is often favored where toxicity is a concern because it is considerably less toxic than lead and several other heavy metals, making it a safer alternative in many consumer and industrial applications. It readily forms colorful, hopper‑style crystals that are popular among collectors. Its combination of high atomic weight, low toxicity and useful metallurgical properties gives bismuth a unique niche among the chemical elements.