Lead Facts – Pb or Element Number 82

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Lead Facts
Key facts about lead include its symbol Pb and atomic number 82.

Lead is a useful element that is also a toxic heavy metal. In everyday life, it occurs in batteries, solder, stoneware, vinyl, and old paint. Here are 10 interesting lead facts, along with its atomic data, properties, uses, and sources.

10 Lead Facts

  1. Lead is the element with atomic number 82. This means each lead atom contains 82 protons, which is the highest number of protons for any stable element. Natural lead is a mix of four stable isotopes, although numerous radioactive isotopes exist. The element’s symbol Pb does not match the element’s current name. Pb comes from the old Latin name for lead of plumbum.
  2. Lead is a basic metal or post-transition metal. Like other metals (except mercury), it is a solid at room temperature. It is a shiny blue-white metal that oxidizes in air until it is dull gray. The liquid is shiny and silvery. Lead is dense, malleable, and ductile like other metals. Unlike most other metals, it is extremely soft, a poor electrical conductor, and has a low melting point.
  3. Of all the metals, lead is the only one that exhibits zero Thomson effect. What this means is that lead neither absorbs nor releases heat when an electrical current passes through it.
  4. Ancient humans knew about lead. Sometimes it is called “the first metal”. In alchemy, lead gets associated with the planet Saturn. Of course, the alchemists quested for a way of turning lead into gold.
  5. Lead has many uses, but over half of the lead purified today finds its way into lead-acid car batteries. While most people know lead occurs in batteries, they may be unaware it also occurs in vinyl and other plastics and some stoneware. The element occurs in pure form naturally, but most lead in use today is recycled from batteries. Galena (PbS) is the main mineral containing lead, but is also occurs in copper, silver, and zinc ores.
  6. Lead is a potent neurotoxin. Its effects are most dangerous to babies and children. Lead is a cumulative toxin, so there really is no safe exposure level.
  7. Distinguishing between lead and tin is a challenge because the two metals share so many common properties. Throughout most of history, the two elements were thought to be different forms of the same substance. The Romans called lead “plumbum nigrum” or black lead, while tin was “plumbum candidum” or bright lead.
  8. Pencil lead is graphite (a form of carbon) and not lead. That being said, lead is sufficiently soft that it leaves a mark on paper or another surface. The Romans called graphite “plumbago” or “act for lead”. Lead actually is closely related to carbon and share several common properties with the element, as they are in the same family.
  9. Another word that takes its cues from lead is “plumbing”. Remember, the old word for lead was plumbum. The ancient Romans used lead to make pipes for plumbing. Hard water scale inside the pipes protected Romans from excessive exposure to the toxic element. In modern times, lead solder welds plumbing fixtures. Whether or not the solder is safe depends on whether the water is hard or soft. Lead has many other uses. Added to gasoline, it reduces engine know. It occurs in paints, bullets, stained glass, crystal, radiation shielding, roofing, and statues. It has largely been phased out in pesticides, cosmetics, and foods. In foods and lipsticks, “sugar of lead” was a (poisonous) non-nutritive sweetener. Lead remains a common contaminant in cosmetics because it naturally occurs with mica (which adds sparkle) and iron oxide (which makes red and brown colors).
  10. Lead is a primordial element, meaning it has been around since the birth of the solar system. Its abundance in the Earth’s crust is 14 parts per million by weight. Unlike some heavy elements, a lot of lead remains in the crust instead of sinking toward the core because lead minerals are relatively lightweight. The element’s abundance in the solar system is 0.121 parts per billion by weight.

Basic Lead Facts

  • Name: Lead
  • Atomic Number: 82
  • Element Symbol: Pb (from Latin plumbum)
  • Discovery: Middle East (7000 BCE)
  • Group: Group 14 (carbon group)
  • Period: Period 6
  • Block: p-block
  • Element Family: post-transition metal (basic metal)
  • Atomic Mass: [206.14, 207.94] or 207.2
  • Electron Configuration: [Xe] 4f14 5d10 6s2 6p2
  • Isotopes: 204Pb (1.4%), 206Pb (24.1%), 207Pb (22.1%), 208Pb (52.4%)

Lead Atomic Data

  • Phase at STP: solid
  • Melting point: 600.61 K ​(327.46 °C, ​621.43 °F)
  • Boiling point: 2022 K ​(1749 °C, ​3180 °F)
  • Density: (near r.t.) 11.34 g/cm3
  • Oxidation states: −4, −2, −1, +1, +2, +3, +4 (an amphoteric oxide)
  • Electronegativity: Pauling scale: 2.33 (in +4), 1.87 (in +2)
  • Ionization energies
    1st: 715.6 kJ/mol
    2nd: 1450.5 kJ/mol
    3rd: 3081.5 kJ/mol
  • Atomic radius: empirical: 175 pm
  • Covalent radius: 146±5 pm
  • Van der Waals radius: 202 pm
  • Heat of fusion: 4.77 kJ/mol
  • Heat of vaporization: 179.5 kJ/mol
  • Molar heat capacity: 26.650 J/(mol·K)

Properties

  • Natural occurrence: primordial
  • Crystal structure: ​face-centered cubic (fcc)
  • Speed of sound (thin rod): 1190 m/s (at room temperature)
  • Thermal expansion: 28.9 µm/(m⋅K) (at 25 °C)
  • Thermal conductivity: 35.3 W/(m⋅K)
  • Electrical resistivity: 208 nΩ⋅m (at 20 °C)
  • Magnetic ordering: diamagnetic
  • Molar magnetic susceptibility: −23.0×10−6 cm3/mol (at 298 K)
  • Young’s modulus: 16 GPa
  • Shear modulus: 5.6 GPa
  • Bulk modulus: 46 GPa
  • Poisson ratio: 0.44
  • Mohs hardness: 1.5
  • Brinell hardness: 38–50 MPa
  • CAS Number: 7439-92-1

References

  • Assi, M. A.; Hezmee, M. N. M.; Haron, A. W.; et al. (2016). “The detrimental effects of lead on human and animal health”. Veterinary World. 9 (6): 660–671. doi:10.14202/vetworld.2016.660-671
  • Baird, C.; Cann, N. (2012). Environmental Chemistry (5th ed.). W. H. Freeman and Company. ISBN 978-1-4292-7704-4.
  • Emsley, John (2011). Nature’s building blocks: An A-Z Guide to the Elements. Oxford University Press. ISBN 978-0-19-960563-7.
  • Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  • Hammond, C. R. (2004). The Elements, in Handbook of Chemistry and Physics (81st ed.). CRC press. ISBN 978-0-8493-0485-9.
  • Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. ISBN 0-8493-0464-4.