Bismuth

Bismuth (Bi) is a post-transition metal with atomic number 83 and an atomic mass of 208.98. Its electron configuration is [Xe] 4f14 5d10 6s2 6p3, which gives it 5 valence electrons.

Bismuth key data

Symbol	Bi
Atomic number	83
Atomic mass (standard atomic weight)	208.98
Molar mass	208.98 g/mol
Protons	83
Neutrons (most abundant isotope, bismuth-209)	126
Electrons (neutral atom)	83
Valence electrons	5
Category	Post-transition metal
Period	6
Group	15
Block	p-block
Noble gas notation	[Xe] 4f14 5d10 6s2 6p3
Full electron configuration	1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p3
Electrons per shell	2, 8, 18, 32, 18, 5

Atomic mass: IUPAC CIAAW abridged standard atomic weights, 2024. Most abundant isotope: NIST Atomic Weights and Isotopic Compositions.

Measured properties of bismuth

From PubChem, the US National Institutes of Health. Public domain. The first ionisation energy is the value for bismuth from the NIST Atomic Spectra Database, in place of PubChem’s 7.289 eV.

Melting point	544.55 K (271.4 °C), 76th of 103 by melting point
Boiling point	1837 K (1563.9 °C), 59th of 93 by boiling point
Density	9.807 g/cm³, 28th of 96 by density
State at room temperature	Solid
Electronegativity	2.02 (Pauling), 29th of 95 by electronegativity
Van der Waals radius	207 pm, joint 52nd of 99 by atomic radius
First ionisation energy	7.2855 eV (702.94 kJ/mol), 49th of 102 by first ionisation energy
Electron affinity	0.946 eV (91.3 kJ/mol), 25th of 57 by electron affinity
Common oxidation states	+5, +3
Discovered	1753

Each rank counts down from the highest value, among the elements PubChem’s table gives one for, and links to that property ranked across the whole table. All of them are collected under periodic trends.

Bismuth electron configuration

The full electron configuration of bismuth is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p3. With the noble-gas core collapsed it is [Xe] 4f14 5d10 6s2 6p3, and the outermost subshell is 6p3.

Bohr model of bismuth (Bi): a nucleus and six shells holding 2, 8, 18, 32, 18 and 5 electrons from the inside out. — Bohr model of bismuth (Bi). Image © ScienceQuest, CC BY 4.0: free to reuse with credit to ScienceQuest and a link to this page, as the image licence explains.

Orbital box diagram of bismuth (Bi), [Xe] 4f14 5d10 6s2 6p3, with the xenon core drawn as one bar: one box per orbital, filled by Hund’s rule, showing three unpaired electrons, in 6p. — Orbital diagram of bismuth (Bi). Image © ScienceQuest, CC BY 4.0: free to reuse with credit to ScienceQuest and a link to this page, as the image licence explains.

Why group and block follow from this is set out in how the periodic table maps electron configuration, and the electron configuration of every element is listed on one page.

Mass of one bismuth atom

A molar mass is grams per mole, so dividing by the Avogadro constant gives the mass of a single atom, or for an element with more than one natural isotope the average mass of its atoms, and the reciprocal gives how many atoms sit in a gram.

Mass of one atom

one atom = 208.98 / (6.02214076 × 10²³)
= 3.4702 × 10⁻²² g

Atoms in one gram

atoms per gram = 6.02214076 × 10²³ / 208.98
= 2.8817 × 10²¹ atoms

Bismuth on the periodic table

Bismuth is in period 6, group 15, in the p-block.

The other elements of group 15 are nitrogen, phosphorus, arsenic, antimony and moscovium.