Tantalum

ChemGlobe: Tantalum - Electronic, thermal, and steric data along with an isotope table.
partisans.spurious.biz/~pkremer/projects/chemglobe/ptoe/_/73.html

ChemicalElements.com: Tantalum - Basic information, atomic structure, and isotopes.
www.chemicalelements.com/elements/ta.html

EnvironmentalChemistry.com: Tantalum - Atomic structure, chemical and physical properties, and table of nuclides.
environmentalchemistry.com/yogi/periodic/Ta.html

It's Elemental: Tantalum - Basic physical and historical information.
education.jlab.org/itselemental/ele073.html

LANL: Tantalum - History, production, properties, and uses.
periodic.lanl.gov/elements/73.html

Lenntech: Tantalum - Physical data, chemical properties, health and environmental effects.
www.lenntech.com/Periodic-chart-elements/Ta-en.htm

Visual Elements: Tantalum - Discovery, uses, physical information, and key isotopes.
www.chemsoc.org/viselements/pages/tantalum.html

Wikipedia: Tantalum - Properties of the element, including its history, applications, and characteristics.
en.wikipedia.org/wiki/Tantalum