QUICK REFERENCE
- Symbol: Pb
- Atomic Number: 82
- Atomic Weight: 207.2
- Element Classification: Post-transition Metal
- Discovered By: Known to ancient civilizations
- Discovery Date: Used by humans for over 6,000 years
- Name Origin: Anglo-Saxon ‘lead’; Latin: ‘plumbum’
- Density(g/cc): 11.34
- Melting Point: 327.46°C
- Boiling Point: 1749°C
- Appearance: Soft, malleable, bluish-white metal
- Atomic Radius(pm): 154
Discovery
Lead has been known and used by humans for thousands of years, making it one of the first metals to be extracted and used by ancient civilizations. Its discovery predates recorded history, with evidence of its use dating back to at least 4000 BC. Lead was widely used in ancient Rome for water pipes and aqueducts, a usage reflected in the chemical symbol Pb, derived from the Latin word ‘plumbum’, meaning lead. The metal was prized for its malleability, resistance to corrosion, and ease of extraction from its ores.
Relation to Other Elements
Lead is a post-transition metal, located in group 14 of the periodic table, sharing the group with carbon, silicon, germanium, tin, and flerovium. Unlike its group neighbors, lead is characterized by its low melting point, softness, and high density. Lead is known for its poor conductivity and resistance to corrosion. It forms stable divalent (Pb2+) compounds and, less commonly, tetravalent (Pb4+) compounds, exhibiting a chemistry that reflects its position at the end of the carbon group.
Natural Occurrence
Lead is rarely found in its elemental form in nature. It primarily occurs in the mineral galena (lead sulfide, PbS), which is the most important lead ore. Other minerals containing lead include anglesite (lead sulfate, PbSO4) and cerussite (lead carbonate, PbCO3). Lead is mined in various parts of the world, with China, Australia, and the United States being among the largest producers.
Uses
Lead has numerous applications, though its use has declined in some areas due to health concerns:
- Batteries: The largest use of lead is in lead-acid batteries for vehicles and emergency power supplies.
- Ammunition: Lead is used in bullets and shot because of its high density, which provides mass for momentum and is easily shaped.
- Radiation Shielding: Lead’s high density and atomic number make it effective at absorbing radiation, making it useful for protective aprons in X-ray rooms and shielding around radioactive materials.
- Construction Materials: Lead is used in roofing, cladding, and as a stabilizer in PVC plastics.
- Alloys: Lead is alloyed with other metals to improve their properties. For example, adding lead to steel or copper improves machinability.
The discovery and widespread use of lead have significantly impacted human civilization, from ancient plumbing systems to modern batteries. However, the recognition of lead’s toxicity, particularly its harmful effects on human health and the environment, has led to increased regulation and a search for safer alternatives in many of its traditional applications.