It's Elemental: Radium - Basic physical and historical information. ChemicalElements.com: Radium - Basic information, atomic structure, and isotopes. EnvironmentalChemistry.com: Radium - Atomic structure, chemical and physical properties, and table of nuclides. Lenntech: Radium - Physical data, chemical properties, health and environmental effects. Wikipedia: Radium - Properties of the element, including its history, applications, and characteristics. Radiochemistry of Radium - Full text of the monograph by Murrell L. Salutsky (W.R. Grace and Co., Research Division, Washington Research Center, Clarksville, Maryland) and H. W. Kirby (Mound Laboratory, Miamisburg, Ohio). WebElements: Radium - Extensive information on history, uses, occurrence, compounds, and properties.