Lead
[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p² · 2 · 8 · 18 · 32 · 18 · 4
A soft heavy metal humanity used in bulk for four thousand years and is now abandoning just as comprehensively. Lead is a cumulative neurotoxin with no safe threshold.
3D model
Bohr model: nucleus and electron shells from the real configuration. Valence electrons are highlighted.
Drag to rotate, scroll to zoom
Atomic properties
- Atomic number
- 82
- Atomic mass
- 207.2 а.е.м.
- Electron configuration
- [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p²
- Electrons per shell
- 2 · 8 · 18 · 32 · 18 · 4
- Block
- p-block
- Group
- Carbon group
- Period
- 6
- Electronegativity (Pauling)
- 1.87
- Electronegativity (Allen)
- 1.85
- Atomic radius
- 154 pm
- Covalent radius
- 146 pm
- Van der Waals radius
- 202 pm
- Ionisation energy 1
- 715.6 kJ/mol
- Ionisation energy 2
- 1 450.5 kJ/mol
- Ionisation energy 3
- 3 081.5 kJ/mol
- Ionisation energy 4
- 4 083 kJ/mol
- Ionisation energy 5
- 6 640 kJ/mol
- Electron affinity
- 34.4 kJ/mol
- Common oxidation states
- +2, +4
- Oxidation states
- -4, -2, -1, +1, +2, +3, +4
Physical properties
- State at 25 °C
- solid
- Density
- 11.34 g/cm³
- Melting point
- 600.61 K · 327.5 °C
- Boiling point
- 2 022 K · 1 748.9 °C
- Speed of sound
- 1 190 m/s
Thermal properties
- Heat of fusion
- 4.77 kJ/mol
- Heat of vaporisation
- 179.5 kJ/mol
- Specific heat capacity
- 0.129 J/(g·K)
- Thermal conductivity
- 35.3 W/(m·K)
Mechanical properties
- Young's modulus
- 16 GPa
- Shear modulus
- 5.6 GPa
- Bulk modulus
- 46 GPa
- Poisson ratio
- 0.44
- Mohs hardness
- 1.5
- Brinell hardness
- 38.3 MPa
Electrical and magnetic properties
- Electrical resistivity
- 208 nΩ·m
- Magnetic ordering
- diamagnetic
- Curie point
- no data
- Néel point
- no data
- Superconducting point
- 7.19 K
Crystal structure
- Crystal structure
- face-centred cubic (fcc)
- Lattice constants
- a = 495.08 pm
Abundance
- In the crust
- 14 mg/kg
- In the ocean
- 3·10⁻⁵ mg/L
- In the universe
- 0.01 mg/kg
- In the human body
- 1.7 mg/kg
Isotopes
| Isotope | Abundance | Half-life | Decay mode |
|---|---|---|---|
| 204Pb | 1.4 % | stable | — |
| 206Pb | 24.1 % | stable | — |
| 207Pb | 22.1 % | stable | — |
| 208Pb | 52.4 % | stable | — |
Lead is the endpoint of all three natural decay series: uranium-238 gives lead-206, uranium-235 lead-207, thorium-232 lead-208. That is what makes uranium-lead dating the most precise method in geochronology.
Discovery
- Year of discovery
- known since antiquity
- Discovered by
- known since antiquity
- Where
- no data
- Origin of the name
- from Latin plumbum; the same root gives plumber and plumb line
History
The Romans made water pipes from lead — Latin plumbum gives both plumb line and plumber. Lead poisoning has been proposed as a cause of Rome's decline, though the evidence is thin.
Where it occurs
14 mg/kg of the crust. The main ore is galena, PbS, usually alongside silver and zinc.
How it is produced
By roasting galena and reducing it in a shaft furnace. Over half of world lead is secondary, from batteries.
Role in living things
No biological role. Lead substitutes for calcium and zinc in enzymes, disrupting haem synthesis and nervous system development.
Safety
There is no safe blood lead level: even low concentrations impair cognition in children. Removing tetraethyl lead from petrol cut average population blood lead several-fold.
Uses
- Lead-acid batteries — over 85 % of consumption
- Radiation shielding: aprons, screens, casks
- Solders (displaced by lead-free in electronics)
- Ballast, counterweights and cable sheathing
Curiosities
- Lead isotope ratios date a rock to within a million years — that is how the age of the Earth was first measured, in 1956.
- Tetraethyl lead was added to petrol from the 1920s to the 2000s, its toxicity known from the start.
- Lead mined before 1945 is prized for ultra-sensitive detectors: it carries no contamination from nuclear testing.
- All three natural decay series end at lead — it is the floor of stability for heavy elements.