Lead

A metallic element with atomic number 82. Symbol Pb, atomic weight 207.19, specific gravity 11.35, melting point 621.32°F (327.4°C), boiling point 3,191°F (1,755°C).

Lead is in column IVA of the periodic table. It has four naturally occurring stable isotopes, lead-204, lead-206, lead-207, and lead-208. The last three of these are all end products of one or another radioactive family.

Lead is one of the first elements known to human societies. It is described in some of the oldest books of the Old Testament and was widely used by some early civilizations. Examples of objects containing lead from fifth millennium Egyptian cultures have been found. The Greeks and Romans also used lead for the manufacture of a variety of tools and containers. Some experts claim that one reason for the decline of the Roman civilization was the extensive use of lead in the empire's water supply system. Lead is now known to have a variety of serious effects on the human nervous system, including diminished mental capacity.

Lead was originally known by its Latin name of plumbum, from which its modern chemical symbol (Pb) is derived. The Latin name is still preserved also in the common names for lead compounds, as in plumbic and plumbous chlorides.