Bismuth at a glance
- Atomic number
- 83
- Symbol
- Bi
- Atomic mass
- 208.98 u
- Category
- Post-transition metal
- Group / period
- 15 / 6
- Electron configuration
- [Xe] 4f 14 5d 10 6s 2 6p 3
- State at 25 °C
- Solid
- Melting point
- 271.6 °C
- Boiling point
- 1564 °C
- Density
- 9.807 g/cm³
- Electronegativity
- 2.02
- 1st ionization energy
- 703 kJ/mol
- Oxidation states
- +3
- Discovered
- Antiquity
Atomic structure
A neutral bismuth atom has 83 protons and 83 electrons, and its most common isotope carries about 126 neutrons. One atom weighs about 3.47 × 10⁻²⁵ kg, so a mole of bismuth (6.022 × 10²³ atoms) weighs 208.98 g. That nucleus holds 1.52 neutrons for every proton, typical of heavy nuclei, which need extra neutrons to hold together against the protons' repulsion. The electrons fill 6 shells (K 2, L 8, M 18, N 32, O 18, P 5), which gives the configuration [Xe] 4f 14 5d 10 6s 2 6p 3. With 5 electrons in its outer shell, it tends to gain or share electrons to complete its outer shell. None of its isotopes is truly stable, but Bi-209 decays so slowly that it is still found in nature.
Physical properties
At room temperature (25 °C) bismuth is a solid. It melts at 271.6 °C and boils at 1564 °C, so it stays liquid across a 1292-degree range. It stays solid in a hot kitchen oven but would melt in a candle flame (about 1000 °C). Its density is 9.807 g/cm³, 9.81 times as dense as water. Its atoms have a radius of about 160 pm (Lead next door is 180 pm). In the solid, its atoms pack into a rhombohedral lattice.
Chemical behaviour
Its electronegativity is 2.02 on the Pauling scale. Pulling off its outermost electron takes 703 kJ/mol, less than Antimony above it (834 kJ/mol). A bond between bismuth and chlorine would be polar covalent, with an electronegativity difference of 1.1. It releases 91 kJ/mol when it gains an extra electron. Its common oxidation states are +3, so in compounds you will usually meet it as Bi³⁺. Group 15 also holds Nitrogen, Phosphorus, Arsenic, Antimony and Moscovium, which share its outer-shell pattern. Its Lewis symbol is Bi surrounded by 5 dots.
Where it comes from
It makes up 0.0085 mg/kg of Earth's crust, the 71st most abundant element there. It has been known since ancient times, one of only 11 elements people used before modern chemistry.