Astatine
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| Name | Astatine |
| Atomic number | 85 |
| Category | Halogen |
| Appearance | Unknown (predicted metallic or black) |
| Discovered | 1940 |
| Discovered by | Dale R. Corson, K. R. MacKenzie, Emilio Segrè |
Astatine Astatine is a radioactive chemical element with atomic number 85, classified among the halogens and notable for extreme rarity and short-lived isotopes. First characterized in 1940, astatine occupies a position near Tellurium and Iodine in the periodic table and has been investigated in contexts linked to Manhattan Project–era research, Los Alamos National Laboratory studies, and modern Oak Ridge National Laboratory and Lawrence Berkeley National Laboratory facilities. Due to its radioactivity, astatine appears primarily in nuclear chemistry, radiopharmacy, and targeted radiotherapy research connected to institutions such as Memorial Sloan Kettering Cancer Center, Mayo Clinic, and cancer centers participating in National Institutes of Health–funded trials.
Introduction
Astatine was first synthesized in experiments conducted by researchers including Emilio Segrè, Dale R. Corson, and K. R. MacKenzie in 1940 following theoretical predictions related to the periodic work of scientists like Dmitri Mendeleev and experimental programs at University of California, Berkeley. Naming debates invoked figures such as Isidor Isaac Rabi and organizations like the International Union of Pure and Applied Chemistry before the current name was adopted. Its discovery intertwined with wartime scientific mobilization at sites including University of Rochester and laboratories collaborating with Radiation Laboratory, MIT and industrial partners.
Physical and Chemical Properties
Astatine's macroscopic properties remain poorly determined because bulk samples are unobtainable; theoretical and extrapolative studies draw on trends observed in Fluorine, Chlorine, Bromine, Iodine, and neighboring elements like Bismuth and Polonium. Predicted properties include metalloid or metallic behavior with a possible dark appearance similar to Tellurium or Polonium. Chemical behavior in solution has been probed using tracer techniques developed in laboratories such as Institut Curie and Karolinska Institute, showing analogies and divergences from Iodine chemistry in reactions studied by groups at Max Planck Society and CNRS. Coordination chemistry experiments using ligands studied at Imperial College London and ETH Zurich indicate multiple oxidation states, with athanatic chemistry comparisons invoking compounds researched at Princeton University and University of Cambridge.
Isotopes and Nuclear Properties
Astatine has no stable isotopes; dozens of radioisotopes have been synthesized at accelerator centers like CERN, GSI Helmholtz Centre for Heavy Ion Research, and TRIUMF. Commonly studied isotopes include mass numbers produced at Joint Institute for Nuclear Research and through decay chains involving nuclides from Uranium and Thorium series observed by teams at Lawrence Livermore National Laboratory. Nuclear decay modes include alpha decay and beta decay with half-lives ranging from milliseconds to hours; notable isotopes in medical research are produced via cyclotrons akin to those operated by Brookhaven National Laboratory and Paul Scherrer Institute. Nuclear models developed by researchers connected to Los Alamos National Laboratory and theories advanced at Oak Ridge National Laboratory inform predictions of shell effects, magic numbers explored by collaborations including Argonne National Laboratory and Rutherford Appleton Laboratory.
Occurrence and Production
Naturally, astatine is generated in trace amounts through decay of heavier elements in uranium and thorium ores studied at mining sites tied to companies like Rio Tinto and historical deposits near Shinkolobwe Mine; concentrations are vanishingly low in Earth's crust according to surveys by United States Geological Survey and analyses by Geological Survey of Canada. Artificial production routes use particle accelerators and reactors at facilities including CERN, TRIUMF, RIKEN, and university cyclotrons affiliated with Johns Hopkins University and McMaster University. Chemical separation and tracer techniques deployed by teams at Argonne National Laboratory and Brookhaven National Laboratory isolate astatine for short-term experiments and radiopharmaceutical preparation performed in hospital settings like Massachusetts General Hospital and Johns Hopkins Hospital.
Applications and Uses
Practical uses of astatine are limited by scarcity and radioactivity; however, targeted alpha-particle therapy research uses astatine-211 produced at cyclotrons similar to those at Paul Scherrer Institute and TRIUMF for oncological treatments investigated at Memorial Sloan Kettering Cancer Center, Mayo Clinic, and University of Pennsylvania Health System. Radiochemical methodologies developed at University of Helsinki and Karolinska Institute enable conjugation of astatine to biomolecules, paralleling work on radioisotopes at UCLA and Dana-Farber Cancer Institute. Experimental nuclear physics studies at GSI Helmholtz Centre and GANIL use astatine isotopes to probe nuclear structure, informing theoretical frameworks shaped at CERN and Los Alamos National Laboratory.
Safety and Environmental Impact
Astatine's radiological hazards are significant despite tiny quantities handled: radioprotection protocols from organizations like International Atomic Energy Agency, World Health Organization, and National Council on Radiation Protection and Measurements guide laboratory and medical use. Environmental mobility is assessed in the context of decay products related to Uranium and Thorium mining legacies overseen by agencies such as Environmental Protection Agency and Natural Resources Canada; remediation practices draw on standards from Nuclear Regulatory Commission and international best practices promoted by International Atomic Energy Agency. Occupational exposure limits, monitoring, and waste management procedures referenced by Occupational Safety and Health Administration and hospital radiation safety offices are essential when producing or using astatine isotopes in clinical or research settings.