See also:

• Science: Chemistry: Elements: Actinides  (2)

ChemGlobe: Actinium: - Electronic, thermal, and steric data along with an isotope table.

ChemicalElements.com: Actinium: - Basic information, atomic structure, and isotopes.

EnvironmentalChemistry.com: Actinium: - Atomic structure, properties, and table of nuclides.

It's Elemental: Actinium: - Basic physical and historical information.

LANL: Actinum: - Basic information and history.

Lenntech: Actinium: - Physical data, chemical properties, health and environmental effects.

Visual Elements: Actinium: - Image, sources, biological role, key isotopes, and oxidation states.

Wikipedia: Actinium: - Details the properties of the element, including its history, applications, and characteristics.