Bismuth (Bi)
Bismuth (Bi) is a post-transition metal with atomic number 83 and a standard atomic weight of 208.98. At room temperature it is a solid that melts at 271 °C and boils at 1,564 °C.
Bismuth key facts
Bismuth at a glance
Identity
| Symbol | Bi |
|---|---|
| Atomic number (Z) | 83 |
| Atomic weight | 208.98 ± 0.01 (CIAAW 2024) |
| Category | Post-transition metal |
| Group | 15 — pnictogens (nitrogen group) |
| Period | 6 |
| Block | p-block |
| CAS number | 7440-69-9 |
Atomic properties
| Electron configuration | [Xe] 4f14 5d10 6s2 6p3 Full: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p3 |
|---|---|
| Electrons per shell | 2, 8, 18, 32, 18, 5 |
| Oxidation states | +3 Less common: -3, -2, -1, 0, +1, +2, +4, +5 |
| Electronegativity (Pauling) | 2.02 |
| First ionisation energy | 7.285 eV (702.9 kJ/mol) 2nd: 16.703 eV · 3rd: 25.571 eV |
| Electron affinity | 0.942 eV |
| Atomic radius (empirical) | 160 pm |
| Covalent radius | 151 pm |
| Van der Waals radius | 207 pm |
Physical properties
| State at 25 °C | Solid |
|---|---|
| Melting point | 271.4 °C · 520.5 °F · 544.55 K |
| Boiling point | 1,564 °C · 2,847.2 °F · 1,837.15 K |
| Density | 9.79 g/cm³ |
| Specific heat capacity | 0.122 J/(g·K) |
| Thermal conductivity | 7.9 W/(m·K) |
| Crystal structure | Rhombohedral |
Isotopes & abundance
| Natural occurrence | Primordial |
|---|---|
| Radioactive | No |
| Natural isotopes (abundance) | 209Bi 100% (radioactive) |
| Stable isotopes | 0 |
| Known isotopes | 41 |
| Abundance in Earth's crust | 0.0085 mg/kg |
| Abundance in seawater | 0.00002 mg/L |
Atomic weights: CIAAW Abridged Standard Atomic Weights 2024. Other properties: standard reference compilations, checked October 2026; predicted values are marked.
Bismuth electron configuration
Bismuth has 83 electrons. Written in short form, its ground-state configuration is [Xe] 4f14 5d10 6s2 6p3 — the electrons of the noble gas xenon, plus 4f14 5d10 6s2 6p3.Written out in full: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p3.
As a member of group 15 it has 5 valence electrons in its outer shell (shell 6), which largely decide its chemistry.
Discovery and name
c. 1500 — Known by the 15th century; shown to be distinct from lead by Claude François Geoffroy (1753) · Europe.
German Wismut (origin uncertain).
Known for
Its only primordial isotope is so slightly radioactive (half-life about 2 × 10¹⁹ years) that it is treated as stable. Used in pink stomach remedies and lead-free solders.
Isotopes of bismuth
Naturally occurring bismuth is a mix of 1 isotope. Each has 83 protons; they differ in the number of neutrons:
| Isotope | Protons | Neutrons | Natural abundance | Stability |
|---|---|---|---|---|
| 209Bi | 83 | 126 | 100% | radioactive · half-life 20.1 × 10¹⁸ years |
41 isotopes of bismuth are known in our data set (half-lives as published in nuclear data tables).
Bismuth compared with group 15
The other elements in group 15 (pnictogens (nitrogen group)), from top to bottom of the table:
| Element | Z | Atomic weight | Melting point | Boiling point | Density | Electronegativity |
|---|---|---|---|---|---|---|
| Nitrogen | 7 | 14.007 | -210 °C | -196 °C | 1.2506 g/L | 3.04 |
| Phosphorus | 15 | 30.974 | 44 °C | 281 °C | 1.823 g/cm³ | 2.19 |
| Arsenic | 33 | 74.922 | — | 614 °C | 5.75 g/cm³ | 2.18 |
| Antimony | 51 | 121.76 | 631 °C | 1,587 °C | 6.68 g/cm³ | 2.05 |
| Bismuth | 83 | 208.98 | 271 °C | 1,564 °C | 9.79 g/cm³ | 2.02 |
| Moscovium | 115 | [290] | — | — | 13.5 g/cm³ (pred.) | — |