Lead

Key information

Atomic number:

Atomic weight:

207

Density:

11400 kg/m³

Boiling point:

1998.16° K

Melting point:

600.56° K

Heat vapour:

176.72 kJ/mol

Heat fusion:

5.11 kJ/mol

Thermal conductivity:

4.6 W/m/K

Specific heat capacity:

34.76 J/kg/K

Lead is a relatively poor conductor of electricity; it is highly resistant to corrosion, but tarnishes on contact with air. Isotopes of lead are the end product of decay in each of three series of naturally occurring radioactive elements.

Alchemy

Lead is one of seven planetary metals known to the Ancients. The manufacture of paint from lead occurred in the Roman world. Being dominated by a particular planet, the planetary metals are each associated with the symbol for their planet. Thus the Swedish pharmacist and chemist Carl Wilhelm Scheele, in the 18th century, uses the planetary symbol for Saturn to represent lead.

Lead is likely to have been used in early times in the reduction process for silver. It is mentioned in holy scriptures, thus:- Jeremiah (vi, 29-30), "The bellows are burned, the lead is consumed of the fire; the founder melteth in vain; for the wicked are not plucked away. Reprobate silver shall men call them because the Lord hath rejected them."

Valency: