Lead
Lead (/lɛd/) is a chemical element in the carbon group with symbol Pb (from Latin:plumbum) and atomic number 82. Lead is a soft, malleable and heavy post-transition metal. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed to air.
Identity
- Atomic mass
- [206.14, 207.94] u
- Category
- Post-transition metals
- Group
- 14
- Period
- 6
- Block
- p
- Oxidation States
- +2, +4
- Phase (25 °C)
- Solid
- Appearance
- metallic gray
Electronic Structure
- Electron configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p2
- Short configuration
- [Xe] 4f14 5d10 6s2 6p2
- Electrons per shell
- 2, 8, 18, 32, 18, 4
- Electronegativity (Pauling)
- 1.87
- Electron affinity
- 34.4 kJ/mol
- 1st ionization energy
- 716 kJ/mol
- Ionization energies
- 716 · 1451 · 3082 · 4083 · 6640 kJ/mol
Physical properties
- Melting point
- 327.5 °C (601 K)
- Boiling point
- 1748.8 °C (2022 K)
- Density
- 11.34 g/cm³
- Molar heat capacity
- 26.6 J/(mol·K)
Chemical behavior of lead
Lead has an electronic configuration [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p². Its oxidation states are +2 (plumbous) and +4 (plumbic), with the +2 state much more stable than +4 due to the 'quantum inert pair effect' that strongly retains the two 6s orbital electrons. It is a soft post-transitional metal, extremely dense, malleable, and dull grey-blue in colour. Newly cut it has a silver-grey shine that rapidly tarnishes due to formation of a passive basic carbonate film. It resists concentrated sulfuric acid thanks to precipitation of an insoluble lead sulfate film.
Reactivity
Pb + H₂SO₄ → PbSO₄ + H₂
It is superficially attacked by sulfuric acid, but the reaction stops immediately at formation of an impermeable protective film of insoluble lead sulfate.
2 Pb + O₂ + 2 H₂O + 2 CO₂ → 2 PbCO₃·Pb(OH)₂
In presence of moist air and carbon dioxide it corrodes superficially forming basic lead carbonate (white lead) that passivates.
PbO₂ + Pb + 2 H₂SO₄ ⇌ 2 PbSO₄ + 2 H₂O
Reversible electrochemical reaction that underpins storage and discharge of electrical energy in lead-acid automotive batteries.
Pb + 2 HCl → PbCl₂ + H₂
It dissolves very slowly in hot hydrochloric acid, precipitating white needle-shaped crystals of lead chloride upon cooling.
Notable compounds
| Compound | Formula | Use or importance |
|---|---|---|
| Lead dioxide | PbO₂ | Dark brown solid with energetic oxidising properties that acts as active material of positive plate in lead-acid batteries |
| Lead tetroxide | Pb₃O₄ | Minio; traditional reddish-orange pigment used historically in anti-corrosive paints and priming for bridges and iron structures |
| Lead acetate ("sugar of lead") | Pb(CH₃COO)₂·3H₂O | Soluble salt with very sweet and toxic taste used in ancient Rome to sweeten wines (sapa) |
| White lead | 2PbCO₃·Pb(OH)₂ | Oil white pigment with great opacity used by Renaissance masters since the Renaissance |
Electron shell distribution
View in the atom builderIsotopes
Natural lead is composed of four isotopes: three of terminal radiogenic origin (²⁰⁶Pb with 24.1%, from uranium-238 chain; ²⁰⁷Pb with 22.1%, from uranium-235 chain; and ²⁰⁸Pb with 52.4%, from thorium-232 chain) and a primordial non-radiogenic isotope, lead-204 (²⁰⁴Pb, 1.4%). Lead-208 is a doubly magic nucleus (82 protons and 126 neutrons), which makes it the most massive and heavy stable nuclide that exists in the universe.
Occurrence and production
It is a relatively abundant element for its high atomic mass (about 13-14 ppm in Earth's crust). Rarely appears free. Its primary undisputed mineral is Galena (lead sulfide, PbS), recognisable by its cubic plumbous metallic lustre and high density; other secondary sources are Cerussite (lead carbonate) and anglesite (lead sulfate). The world's main producers are China, Australia and the United States. It is obtained by roasting the galena to lead oxide and reducing it with coke in blast furnaces, followed by Betts electrolytic refining.
History and origin of the name
It is one of the most anciently known metals (more than 7,000 years). Ancient Rome exploited it massively to manufacture water pipes ('fistulae'), heat baths, make heavy projectiles and as a sweetening additive to wines (lead acetate or sapa). Its chemical symbol Pb comes from the Latin word 'plumbum', a term from which the words 'plumber' or 'plumber' (lead pipes) derive.
Applications and relevance of lead
Uses of the element
More than 85% of the lead consumed in the world is dedicated to the manufacture of rechargeable lead-acid accumulators for car starting and lighting batteries, forklifts and uninterruptible power supplies (UPS). Due to its high density and atomic number, it is the standard shielding against ionising radiation in medical X-ray rooms, nuclear medicine and radioactive waste containers.
Uses of its compounds
Historically it was added as an anti-knock agent to petrol in the form of tetraethyllead (prohibited worldwide in 2021) and in household paint pigments. Currently, lead salts are used in perovskite semiconductors for the latest generation solar cells and lead crystal optical glass.
Health, safety and environment
Biological role
It performs no known physiological function and is a serious multi-organ toxin. Lead mimics calcium and iron, competing with them and blocking the delta-aminolevulinic acid dehydratase (ALAD) enzyme, which inhibits haemoglobin synthesis and causes microcytic anaemia.
Safety
Chronic lead poisoning is called 'saturnism'. In children it causes irreversible brain damage, loss of intelligence quotient, hyperactivity and behavioural problems; in adults it causes hypertension, chronic kidney damage and peripheral neuropathy with 'drop hand'. There is no safe level of lead in blood.
Environment
Combustion of leaded petrol during the 20th century dispersed millions of tonnes of lead particles in the global atmosphere into Greenland ice. Lead shot in wetlands causes avian lead poisoning in waterfowl, which has led to its use being banned in hunting ammunition.
Frequently asked questions about Lead
Why is lead-208 the heaviest stable atomic nucleus that exists in nature?
In nuclear physics, nuclei containing a closed number of nucleons ('magic numbers') enjoy spherical symmetry and exceptionally strong binding energy. Lead-208 has exactly eighty-two protons and one hundred and twenty-six neutrons, completing closed quantum levels in both species. This 'doubly magic' configuration gives it absolute nuclear stability, constituting the indestructible endpoint where radioactive decay chains of heavier elements such as thorium end.
How did Clair Patterson determine the exact age of the Earth by studying lead contamination?
In 1953, geochemist Clair Patterson analysed the lead isotopic proportions of the Canyon Diablo meteorite to calculate the age of the Earth at 4.55 billion years. During his research, he discovered that terrestrial samples were massively contaminated by environmental lead generated by leaded petrol. His tenacious scientific fight demonstrated that human blood lead levels had soared hundreds of times, achieving worldwide prohibition of tetraethyllead.
How does the electrochemical reaction of lead-acid batteries work in cars?
The lead-acid battery consists of spongy lead metal plates (anode) and lead dioxide plates (cathode) immersed in dilute sulfuric acid. During engine starting, lead at the anode oxidises to lead sulfate while lead dioxide at the cathode is also reduced to lead sulfate, releasing a massive current flow. When the car alternator works, the electric current reverses the chemical process, regenerating the original electrodes.
How does lead poisoning affect children's brains and cognitive performance?
In young children with developing brains, lead ions (Pb²⁺) easily cross the immature blood-brain barrier mimicking calcium. They enter neuronal synapses and interfere with neurotransmitter release and synaptic plasticity in the prefrontal cortex and hippocampus. This induces neuronal apoptosis, irreversible loss of intelligence quotient points, reduced concentration, hyperactivity disorders and greater tendency to aggressive behaviours in adolescence.
Why did ancient Romans use lead to sweeten wine?
In ancient Rome it was common to boil grape must in lead pots to obtain a thick syrup called 'defrutum'. The acidity of the fruit dissolved part of the metal forming lead acetate, a compound with a very pleasant sweet taste known as 'sugar of lead'. Its daily consumption caused chronic saturnism among patricians, causing abdominal pain, gout and cognitive decline without them knowing the cause.
Why do we wear a lead apron at the dentist when we have dental X-rays?
X-rays are high-energy electromagnetic radiation capable of passing through soft tissues. To protect the body parts that do not need to be examined, lead aprons and screens are used. Being a metal with many protons and great density, its electrons absorb and scatter radiation, preventing it from reaching sensitive organs such as the thyroid or reproductive cells.
Why are lead-based perovskites revolutionising solar panels?
The hybrid perovskites that contain lead (such as methylammonium lead triiodide) are semiconductor materials with astonishing light absorption coefficients and amazing tolerance to atomic defects in their crystal lattice. In just ten years of research, their photovoltaic efficiency in the laboratory has jumped from 3% to more than 26%. Combined in tandem with silicon solar cells, they surpass conventional solar panel performance limits by a wide margin.
Main sources consulted: PubChem, Royal Society of Chemistry, NIST, IUPAC. Last revision: November 2026.