Websites on Barium:
ChemGlobe: Barium
Electronic, thermal, and steric data, along with an isotope table.
ChemicalElements.com: Barium
Basic information, atomic structure, and isotopes.
EnvironmentalChemistry.com: Barium
Atomic structure, chemical and physical properties, and table of nuclides.
It's Elemental: Barium
Basic physical and historical information.
LANL: Barium
History, sources, properties, and uses.
Lenntech: Barium
Physical data, chemical properties, health and environmental effects.
Visual Elements: Barium
Image, appearance, source, uses, key isotopes, and ionisation energies.
WebElements: Barium
Extensive information on history, uses, occurrence, compounds, and properties.
Wikipedia: Barium
Properties of the element, including its history, applications, and characteristics.