Overview and basic data.

Explanation with photographs.

Atomic structure, properties, and table of nuclides.

Basic physical and historical information.

Basic information, atomic structure, and table of isotopes.

Numeric data, uses, and general information.

Data tables and historic information.

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

Extensive information on history, uses, occurrence, compounds, and properties of the element.

Physical data, chemical properties, health and environmental effects.