Britannica Nobel Prize: Radium
   Detailed overview and data.
   http://www.britannica.com/nobel/micro/491_93.html

ChemGlobe: Radium
   Electronic, thermal, and steric data along with an isotope table.
   http://partisans.spurious.biz/~pkremer/projects/chemglobe/ptoe/_/88.html

ChemicalElements.com: Radium
   Basic information, atomic structure, and isotopes.
   http://www.chemicalelements.com/elements/ra.html

EnvironmentalChemistry.com: Radium
   Atomic structure, chemical and physical properties, and table of nuclides.
   http://environmentalchemistry.com/yogi/periodic/Ra.html

It's Elemental: Radium
   Basic physical and historical information.
   http://education.jlab.org/itselemental/ele088.html

LANL: Radium
   History, sources, properties, and uses.
   http://periodic.lanl.gov/elements/88.html

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

Radiochemistry of Radium
   Full text of the monograph by Murrell L. Salutsky (W.R. Grace & Co., Research Division, Washington Research Center, Clarksville, Maryland) and H. W. Kirby (Mound Laboratory, Miamisburg, Ohio). [PDF]
   http://lib-www.lanl.gov/cgi-bin/getfile?rc000041.pdf

Visual Elements: Radium
   Image, general and physical information, source, uses, key isotopes, and ionisation energies.
   http://www.chemsoc.org/viselements/pages/radium.html

Wikipedia: Radium
   Properties of the element, including its history, applications, and charateristics.
   http://en.wikipedia.org/wiki/Radium