Basic information, atomic structure, and isotopes.

Atomic structure, chemical and physical properties, and table of nuclides.

Basic physical and historical information.

History, sources, properties, and uses.

Physical data, chemical properties, health and environmental effects.

Full text of the monograph by James Armstrong (Florida State University, Tallahassee, Florida). [PDF]

Data tables and historic information.

General and physical information, source, uses, key isotopes, and ionisation energies.

Extensive information on history, uses, occurrence, compounds, and properties.

Properties of the element, including its history, applications, and characteristics.