Bismuth (Bi)
Element 83 · Post-transition metal · atomic mass 208.98 u · group 15, period 6
Electron shells: 2, 8, 18, 32, 18, 5
Bismuth is the heaviest element that is effectively stable — its half-life exceeds the age of the universe by a billion times. It is remarkably non-toxic for a heavy metal, which is why it is in stomach medicine.
Bismuth is technically radioactive, but a sample takes about a billion times the age of the universe to half decay.
- Atomic number
- 83
- Atomic mass
- 208.98 u
- Electron configuration
- [Xe] 6s² 4f¹⁴ 5d¹⁰ 6p³
- Group · period · block
- 15 · 6 · p
- Oxidation states
- +3, +5
- Electronegativity
- 2.02 (Pauling)
- Melting point
- 271 °C
- Boiling point
- 1,564 °C
- Density
- 9.807 g/cm³
- State at 20 °C
- Solid
- Appearance
- Silvery-pink, brittle metal
- Discovered
- Claude François Geoffroy, 1753
83 protons, and 83 electrons when neutral
IUPAC standard atomic weight
Pnictogens
What Bismuth is used for
- Stomach remedies (bismuth subsalicylate)
- Lead-free solders and plumbing fittings
- Cosmetics and pigments
- Fire sprinkler fusible alloys
Atomic structure of Bismuth
A neutral bismuth atom has 83 protons and 83 electrons. Its most common isotope carries about 126 neutrons, which is where the mass number 209 comes from. Change the neutron count and you have a different isotope of bismuth; change the proton count and you have a different element entirely.
Those electrons fill shells from the inside out: 2, 8, 18, 32, 18, 5. In orbital notation that is [Xe] 6s² 4f¹⁴ 5d¹⁰ 6p³, leaving 5 valence electrons in the outer shell — the ones that do the chemistry.
3D electron orbitals
See where Bismuth's electrons actually are — a cloud of 26,000 points sampled from the probability density |ψ|², not a cartoon of a lobe.
Where Bismuth sits in the periodic table
Metals to the right of the d-block. Softer, lower-melting and more brittle than the transition metals, with more covalent character in their bonding.
Discovery and naming
Bismuth was discovered by Claude François Geoffroy in 1753. Its name comes from German Wismut, of uncertain origin.
Keep exploring
Atomic weight from IUPAC/CIAAW; physical properties from PubChem (US National Library of Medicine). Values that have never been measured are shown as “not measured” rather than estimated.
Related Calculators
Frequently Asked Questions
What is the atomic mass of Bismuth?
The standard atomic weight of Bismuth is 208.98 u, as published by IUPAC's Commission on Isotopic Abundances and Atomic Weights.
How many protons, neutrons and electrons does Bismuth have?
Bismuth has 83 protons, because the atomic number is the proton count and that is what makes an atom Bismuth at all. A neutral Bismuth atom has the same number of electrons, 83. The neutron count varies by isotope; the most common one has about 126, since 209 − 83 = 126.
What is the electron configuration of Bismuth?
The electron configuration of Bismuth is [Xe] 6s² 4f¹⁴ 5d¹⁰ 6p³. Its electrons are arranged 2, 8, 18, 32, 18, 5 across 6 shells.
Is Bismuth a metal?
Yes. Bismuth is classified as a post-transition metal, on the metallic side of the table.
What group and period is Bismuth in?
Bismuth is in group 15 (the pnictogens), period 6, in the p-block. The group is its column and the period is its row.
What is the charge of Bismuth?
Bismuth most commonly forms a 3+ ion. It has 5 outer electrons available to lose. Across all its compounds it shows oxidation states of +3, +5.
What is the melting point of Bismuth?
Bismuth melts at 271 °C and boils at 1,564 °C. That puts it in the solids at everyday temperatures.
What is Bismuth used for?
Stomach remedies (bismuth subsalicylate), Lead-free solders and plumbing fittings, Cosmetics and pigments, Fire sprinkler fusible alloys. Bismuth is the heaviest element that is effectively stable — its half-life exceeds the age of the universe by a billion times.
Who discovered Bismuth, and where does its name come from?
Bismuth (Bi) was discovered by Claude François Geoffroy in 1753. The name comes from German Wismut, of uncertain origin.