Britannica Nobel Prize: Astatine
Overview and basic data.
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.
It's Elemental: Astatine
Basic physical and historical information.
Lenntech: Astatine
Physical data, chemical properties, and health effects.
Radiochemistry of Astatine
Full text of the monograph by Evan H. Appelman (Argonne National Laboratory, Lemont, Illinois). [PDF]
Visual Elements: Astatine
General and physical information, source, key isotopes, and ionisation energies.
WebElements: Astatine
Extensive information on history and properties.
Wikipedia: Astatine
Properties of the element, including its history, applications, and characteristics.