Bismuth (Bi)

Bismuth was assumed to be the heaviest stable element until 2003, when a French team measured its alpha decay: bismuth-209 has a half-life of about 2 × 10¹⁹ years, roughly a billion times the age of the universe, so it is radioactive in the same sense that a bank vault is technically openable. It expands as it freezes, like water and unlike almost every other metal, which is why it was used in type metal. Grown slowly from a melt it forms iridescent stair-stepped hopper crystals whose colours come from an oxide film, and it is the most strongly diamagnetic element — a bismuth block visibly repels a strong magnet.

Properties

Atomic number

83

Symbol

Bi

Standard atomic weight

208.98 u

Category

Post-transition metal

Group

15

Period

6

Block

p-block

Electron configuration

[Xe] 6s² 4f¹⁴ 5d¹⁰ 6p³

Electrons per shell

2, 8, 18, 32, 18, 5

Melting point

544.55 K — 271.4 °C — 520.5 °F

Boiling point

1,837 K — 1563.8 °C — 2846.9 °F

Density

9.807 g/cm³

Electronegativity

2.02 (Pauling)

Oxidation states

+3, +5

Discovered

1753 by Claude François Geoffroy

Electron configuration

Full

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p³

Noble gas shorthand

[Xe] 6s² 4f¹⁴ 5d¹⁰ 6p³

Shells

K: 2 · L: 8 · M: 18 · N: 32 · O: 18 · P: 5

What it is used for

• Bismuth subsalicylate — the pink stuff for upset stomachs
• Lead-free solder, plumbing fittings and free-machining brass
• Low-melting alloys for fire sprinkler links and fusible plugs
• Bismuth oxychloride, the pearlescent pigment in cosmetics
• Radiation shielding aprons, as a lead substitute

Practically stable but formally radioactive: the alpha decay of bismuth-209 was detected in 2003 with a half-life around 2 × 10¹⁹ years. IUPAC still publishes a standard atomic weight for it, unlike the genuinely radioactive elements that follow.

Neighbours in the table

Group 15

Elements in the same group share their outer electron count, which is why they behave similarly in reactions. Bismuth sits in group 15 with nitrogen, phosphorus, arsenic, antimony, moscovium.