Ackerman Chem F

Lead—a metal that archaeological discoveries prove was used at least 5,000 years ago—is the heaviest element in Group 14 of the periodic table, a group often known as the carbon family. It is a metallic element with atomic number 82, with symbol Pb, atomic weight 207.19, specific gravity 11.35, melting point 621.32°F (327.4°C), and boiling point 3,191°F (1,755°C).

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.

Lead is a heavy, ductile, soft, grayish solid. It can be cast and fabricated easily and has the unusual ability to absorb sound and other forms of vibration. Although it is dissolved by dilute nitric acid, it tends to be resistant to other forms of acid solutions.

Name: Cobalt Symbol: Co Atomic number: 27 Atomic weight: 58.933195 (5) Standard state: solid at 298 K CAS Registry ID: 7440-48-4 Group in periodic table: 9 Group name: (none) Period in periodic table: 4 Block in periodic table: d-block Colour: lustrous, metallic, greyish tinge Classification: Metallic

Cobalt is a ferromagnetic metal. Pure cobalt is not found in nature, but compounds of cobalt are common. Small amounts of it are found in most rocks, soil, plants, and animals.

The Curie temperature is 1115 °C, and the magnetic moment is 1.6–1.7 Bohr magnetons per atom. In nature, it is frequently associated with nickel, and both are characteristic minor components of meteoric iron. Mammals require small amounts of cobalt which is the basis of vitamin B12. Cobalt-60, an artificially produced radioactive isotope of cobalt, is an important radioactive tracer and cancer-treatment agent. Cobalt has a relative permeability two thirds that of iron. Metallic cobalt occurs as two crystallographic structures: hcp and fcc. The ideal transition temperature between hcp and fcc structures is 450 °C, but in practice, the energy difference is so small that random intergrowth of the two is common.