It's Elemental: Astatine - Basic physical and historical information. Chemical Elements.com: Astatine - Basic information, atomic structure, and table of isotopes. EnvironmentalChemistry.com: Astatine - Atomic structure, chemical and physical properties, and table of nuclides. Lenntech: Astatine - Physical data, chemical properties, and health effects. Wikipedia: Astatine - Properties of the element, including its history, applications, and characteristics. Radiochemistry of Astatine - Full text of the monograph by Evan H. Appelman (Argonne National Laboratory, Lemont, Illinois). WebElements: Astatine - Extensive information on history and properties. Visual Elements: Astatine - General and physical information, source, key isotopes, and ionisation energies.