Skip to Main Content

About Astatine

Astatine Bohr

With less than one gram present on earth at any given time, radioactive Astatine is the second rarest naturally-occurring element on the periodic table after berkelium, and the rarest of the non-transuranic elements. Only six of astatine’s 37 known isotopes are naturally occurring; trace amounts of those with atomic numbers 214-219 are produced via decay chains of heavier elements like francium and polonium and/or exist in equilibrium with isotopes of uranium, thorium, and neptunium. Its most stable isotope is 210-At, which has a half-life of 8.1 hours and decays to polonium-210; the least stable is 213-At, which decays to the bismuth-209 after only 125 nanoseconds. Given its quick decay, the element has proven difficult to study. Any quantity of astatine sufficient to constitute a solid would vaporize instantaneously from its radioactive energy, so many of its properties are either unknown or estimated. The element is generally considered to be a member of the halogen family based on observed properties obtained via mass spectrometry and radioactive tracer experiments with dilute astatine solutions; it behaves similarly to iodine, though it is more metallic.

Mendeleev’s periodic table contained a blank spot beneath iodine for a theoretical element named “eka-iodine.” Scientists’ subsequent attempts to find the element in nature were fruitless, and the quest to synthesize it in the lab was fraught with false starts. Fred Allison and his team at Alabama Technical Institute (now Auburn University) were the first in a series of researchers to mistakenly claim discovery of the elusive element in 1931; their discredited “alabamine” was followed by Rajendralal De’s “dakin,” Walter Minder’s “helvetium,” and Mitter and Alice Leigh-Smith’s “anglo-helvetium.” In 1940, Berkeley scientists Dale Corson, Kenneth Ross MacKenzie, and Emilio Segrè were finally successful in artificially producing 211-At by bombarding a bismuth sputtering target with alpha particles in a particle accelerator. They named the element astatine from the Greek astatos, meaning “unstable.” Astatine was the second synthetic element to be conclusively identified, technetium having been discovered by Segrè and Carlo Perrier three years earlier.

Corson, MacKenzie, and Segre’s method is still the primary means of synthesizing 209-211At; the bismuth target is first cooled under nitrogen and then heated to vaporize traces of other radioisotopes, allowing the astatine to be distilled and collected on a cold finger. Several compounds of astatine have been synthesized in microscopic amounts: in addition to hydrogen (hydrogen astatide, HAt, which forms hydroastatic acid when dissolved in water), astatine has been shown to bind to the other halides, silver, sodium, palladium, oxygen, sulfur, selenium, nitrogen, lead, boron, and tellurium, as a colloid. The first ionization energy of the astatine atom was unknown until 2013, when CERN scientists used laser spectroscopy to measure it as 9.31751 electron volts (eV), which was confirmed by Canada's national laboratory for particle and nuclear physics TRIUMF.

Astatine-211 is the element’s only commercially viable isotope, its decay properties making it useful as a short-range radiation source for targeted alpha particle therapy in cancer treatment. Like iodine-113, it preferentially accumulates in the thyroid gland, but it decays faster and emits only alpha particles that have less of a tendency to migrate to surrounding tissue than the beta particles emitted by iodine-113.

Astatine Properties

Astatine Bohr ModelAstatine is a Block P, Group 17, Period 6 element. The number of electrons in each of Astatine's shells is 2, 8, 18, 32, 18, 7 and its electron configuration is [Xe] 4f14 5d10 6s2 6p5. The Astatine atom has a covalent radius of and it's Van der Waals radius is In its elemental form, Astatine's CAS number is 7440-68-8 and its appearance is unknown. Astatine is the rarest naturally occurring non-transuranic element. The amount of naturally occurring astatine in the world is about 25g. Astatine was discovered by Dale R. Corson, Kenneth Ross MacKenzie and Emilio Segrè in 1940.

Astatine is highly radioactive. Astatine information, including technical data, safety data, properties, research, applications and other useful facts are specified below. Scientific facts such as the atomic structure, ionization energy, abundance on Earth, conductivity and thermal properties are included.

Symbol: At
Atomic Number: 85
Atomic Weight: 210
Element Category: halogen
Group, Period, Block: 17 (halogens), 6, p
Color: metallic/ Presumed very dark
Other Names: Astat, Astato
Melting Point: 302 °C, 576 °F, 575 K
Boiling Point: 337 °C, 639 °F, 610 K
Density: 6.2–6.5 g/cm3 (predicted)
Liquid Density @ Melting Point: N/A
Density @ 20°C: 7 g/cm3 approx.
Density of Solid: 6400 (estimated) kg·m3
Specific Heat: N/A
Superconductivity Temperature: N/A
Triple Point: N/A
Critical Point: N/A
Heat of Fusion (kJ·mol-1): 23.8
Heat of Vaporization (kJ·mol-1): 585.22
Heat of Atomization (kJ·mol-1): 91
Thermal Conductivity: 1.7 W·m-1·K-1
Thermal Expansion: N/A
Electrical Resistivity: N/A
Tensile Strength: N/A
Molar Heat Capacity: N/A
Young's Modulus: N/A
Shear Modulus: N/A
Bulk Modulus: N/A
Poisson Ratio: N/A
Mohs Hardness: N/A
Vickers Hardness: N/A
Brinell Hardness: N/A
Speed of Sound: N/A
Pauling Electronegativity: 2.2
Sanderson Electronegativity: N/A
Allred Rochow Electronegativity: 1.9
Mulliken-Jaffe Electronegativity: 2.85 (14.3% s orbital)
Allen Electronegativity: N/A
Pauling Electropositivity: 1.8
Reflectivity (%): N/A
Refractive Index: N/A
Electrons: 85
Protons: 85
Neutrons: 125
Electron Configuration: [Xe] 4f14 5d10 6s2 6p5
Atomic Radius: N/A
Atomic Radius,
non-bonded (Å):
Covalent Radius: 150 pm
Covalent Radius (Å): 1.48
Van der Waals Radius: 202 pm
Oxidation States: 7, 5, 3, 1, -1
Phase: Solid
Crystal Structure: N/A
Magnetic Ordering: N/A
Electron Affinity (kJ·mol-1) 270.159
1st Ionization Energy: 887.7±38.59 kJ·mol-1
2nd Ionization Energy: N/A
3rd Ionization Energy: N/A
CAS Number: 7440-68-8
EC Number: N/A
MDL Number: N/A
Beilstein Number: N/A
SMILES Identifier: [At]
InChI Identifier: InChI=1S/At
PubChem CID: 5460479
ChemSpider ID: 4573995
Earth - Total: N/A
Mercury - Total: N/A
Venus - Total: N/A
Earth - Seawater (Oceans), ppb by weight: N/A
Earth - Seawater (Oceans), ppb by atoms: N/A
Earth -  Crust (Crustal Rocks), ppb by weight: N/A
Earth -  Crust (Crustal Rocks), ppb by atoms: N/A
Sun - Total, ppb by weight: N/A
Sun - Total, ppb by atoms: N/A
Stream, ppb by weight: N/A
Stream, ppb by atoms: N/A
Meterorite (Carbonaceous), ppb by weight: N/A
Meterorite (Carbonaceous), ppb by atoms: N/A
Typical Human Body, ppb by weight: N/A
Typical Human Body, ppb by atom: N/A
Universe, ppb by weight: N/A
Universe, ppb by atom: N/A
Discovered By: Dale R. Corson, Kenneth Ross MacKenzie, Emilio Segrè
Discovery Date: 1940
First Isolation: N/A

Astatine Isotopes

Astatine (At) has no stable isotopes. The 32 known isotopes of astatine, ranging from 191At to 223At, are radioactive.

Nuclide Isotopic Mass Half-Life Mode of Decay Nuclear Spin Magnetic Moment Binding Energy (MeV) Natural Abundance
(% by atom)
191At 191 1.7(+11-5) ms Unknown (1/2+) N/A N/A -
193At 192.99984(6) 28(+5-4) ms α to 189Bi (1/2+) N/A 1473.13 -
194At 193.99873(20) ~40 ms α to 190Bi; β+ to 194Po 3+# N/A 1481.21 -
195At 194.996268(10) 328(20) ms α to 191Bi; β+ to 195Po (1/2+) N/A 1489.29 -
196At 195.99579(6) 253(9) ms α to 192Bi; β+ to 196Po 3+# N/A 1497.37 -
197At 196.99319(5) 0.390(16) s α to 193Bi; β+ to 197Po (9/2-) N/A 1505.45 -
198At 197.99284(5) 4.2(3) s α to 194Bi; β+ to 198Po (3+) N/A 1513.53 -
199At 198.99053(5) 6.92(13) s α to 195Bi; β+ to 199Po (9/2-) N/A 1521.6 -
200At 199.990351(26) 43.2(9) s α to 196Bi; β+ to 200Po (3+) N/A 1529.68 -
201At 200.988417(9) 85(3) s α to 197Bi; β+ to 201Po (9/2-) N/A 1547.08 -
202At 201.98863(3) 184(1) s β+ to 202Po; α to 198Bi (2,3)+ N/A 1555.16 -
203At 202.986942(13) 7.37(13) min β+ to 203Po; α to 199Bi 9/2- N/A 1563.23 -
204At 203.987251(26) 9.2(2) min β+ to 204Po; α to 200Bi 7+ N/A 1571.31 -
205At 204.986074(16) 26.2(5) min β+ to 205Po; α to 201Bi 9/2- N/A 1579.39 -
206At 205.986667(22) 30.6(13) min β+ to 206Po; α to 202Bi (5)+ N/A 1587.47 -
207At 206.985784(23) 1.80(4) h EC to 207Po; α to 203Bi 9/2- N/A 1595.55 -
208At 207.986590(28) 1.63(3) h EC to 208Po; α to 204Bi 6+ N/A 1603.63 -
209At 208.986173(8) 5.41(5) h EC to 209Po; α to 205Bi 9/2- N/A 1611.71 -
210At 209.987148(8) 8.1(4) h EC to 210Po; α to 206Bi (5)+ N/A 1619.79 -
211At 210.9874963(30) 7.214(7) h EC to 211Po; α to 207Bi 9/2- N/A 1627.86 -
212At 211.990745(8) 0.314(2) s α to 208Bi; β+ to 212Po; β- to 212Rn (1-) N/A 1626.63 -
213At 212.992937(5) 125(6) ns α to 209Bi 9/2- N/A 1634.71 -
214At 213.996372(5) 558(10) ns α to 210Bi 1- N/A 1642.78 -
215At 214.998653(7) 0.10(2) ms α to 211Bi 9/2- N/A 1650.86 -
216At 216.002423(4) 0.30(3) ms α to 212Bi; β- to 216Rn; EC to 216Po 1- N/A 1649.63 -
217At 217.004719(5) 32.3(4) ms α to 213Bi; β- to 217Rn 9/2- N/A 1657.7 -
218At 218.008694(12) 1.5(3) s α to 214Bi; β- to 218Rn 1-# N/A 1665.78 -
219At 219.011162(4) 56(3) s α to 215Bi; β- to 219Rn 5/2-# N/A 1664.55 -
220At 220.01541(6) 3.71(4) min β- to 220Rn; α to 216Bi 3(-#) N/A 1672.62 -
221At 221.01805(21)# 2.3(2) min β- to 221Rn 3/2-# N/A 1680.7 -
222At 222.02233(32)# 54(10) s β- to 222Rn N/A N/A 1679.46 -
223At 223.02519(43)# 50(7) s Unknown 3/2-# N/A 1687.54 -
Astatine Elemental Symbol

Recent Research & Development for Astatine

  • C. Fry, M. Thoennessen, Discovery of the astatine, radon, francium, and radium isotopes, Atomic Data and Nuclear Data Tables, Volume 99, Issue 5, September 2013
  • Susanta Lahiri, Kamalika Roy, Souvik Sen, Complexation study on no-carrier-added astatine with insulin: A candidate radiopharmaceutical, Applied Radiation and Isotopes, Volume 66, Issue 12, December 2008
  • Kamalika Roy, Susanta Lahiri, Production and separation of Astatine Radionuclides: Some new addition to Astatine Chemistry, Applied Radiation and Isotopes, Volume 66, Issue 5, May 2008
  • Stig Palm, Tom Bäck, Ingela Claesson, Anna Danielsson, Jörgen Elgqvist, Sofia Frost, Ragnar Hultborn, Holger Jensen, Sture Lindegren, Lars Jacobsson, Therapeutic Efficacy of Astatine-211–Labeled Trastuzumab on Radioresistant SKOV-3 Tumors in Nude Mice, International Journal of Radiation Oncology*Biology*Physics, Volume 69, Issue 2, 1 October 2007
  • A. Boskovitz, H. Ochiai, T. Okamura, X.-G. Zhao, D. Bigner, M. Zalutsky, 296 Trastuzumab monoclonal antibody labeled with alpha-particle emitter astatine: targeted radiotherapeutic experiments on a HER2-positive breast carcinomatous meningitis animal model after intrathecal administration, European Journal of Cancer Supplements, Volume 2, Issue 8, September 2004
  • Kamalika Roy, S. Basu, A. Ramaswami, Dalia Nayak, Susanta Lahiri, Incorporation of thiosemicarbazide in Amberlite IRC-50 for separation of astatine from a-irradiated bismuth oxide, Applied Radiation and Isotopes, Volume 60, Issue 6, June 2004
  • Turan Ünak, Some microdosmetric data on Astatine-211, Applied Radiation and Isotopes, Volume 58, Issue 1, January 2003
  • Sture Lindegren, Tom Bäck, Holger J. Jensen, Dry-distillation of astatine-211 from irradiated bismuth targets: a time-saving procedure with high recovery yields, Applied Radiation and Isotopes, Volume 55, Issue 2, August 2001
  • , Project title astatine and iodine radiolabeled monoclonal antibodies, Academic Radiology, Volume 7, Issue 5, May 2000
  • Craig J Reist, Catherine F Foulon, Kevin Alston, Darell D Bigner, Michael R Zalutsky, Astatine-211 labeling of internalizing anti-EGFRvIII monoclonal antibody using N-succinimidyl 5-[211At]astato-3-pyridinecarboxylate, Nuclear Medicine and Biology, Volume 26, Issue 4, May 1999
  • Catherine F Foulon, Kevin L Alston, Michael R Zalutsky, Astatine-211-Labeled Biotin Conjugates Resistant to Biotinidase for Use in Pretargeted Radioimmunotherapy, Nuclear Medicine and Biology, Volume 25, Issue 2, February 1998
  • Michael R. Zalutsky, Michael G. Stabin, Roy H. Larsen, Darell D. Bigner, Tissue distribution and radiation dosimetry of astatine-211-labeled chimeric 81C6, an a-particle-emitting immunoconjugate, Nuclear Medicine and Biology, Volume 24, Issue 3, April 1997
  • Catherine F. Foulon, Bent W. Schoultz, Michael R. Zalutsky, Preparation and biological evaluation of an astatine-211 labeled biotin conjugate: Biotinyl-3-[211At]astatoanilide, Nuclear Medicine and Biology, Volume 24, Issue 2, February 1997
  • Ignace Vergote, Roy H. Larsen, Laure De Vos, Mette Winderen, Turid Ellingsen, Jon Bjørgum, Per Hoff, Magne Aas, Claes Tropé, Kjell Nustad, Distribution of intraperitoneally injected microspheres labeled with the a-emitter astatine (211At) compared with phosphorus (32P) and yttrium (90Y) colloids in mice, Gynecologic Oncology, Volume 47, Issue 3, December 1992
  • R. Ludwig, S. Fischer, R. Dreyer, R. Jacobi, J. Beger, Complex formation equilibria between astatine(I) and sulphur-containing chelating ligands, Polyhedron, Volume 10, Issue 1, 1991
  • L.M. Cobb, A. Harrison, N.E. Dudley, T.E.F. Carr, J.A. Humphreys, Relative concentration of astatine-211 and iodine-125 by human fetal thyroid and carcinoma of the thyroid in nude mice, Radiotherapy and Oncology, Volume 13, Issue 3, November 1988
  • Saed Mirzadeh, Richard M. Lambrecht, Process for producing astatine-211 for radiopharmaceutical use, Environment International, Volume 14, Issue 1, 1988
  • Saed Mirzadeh, Richard M Lambrecht, Process for producing astatine-211 for radiopharmaceutical use, International Journal of Radiation Applications and Instrumentation. Part B. Nuclear Medicine and Biology, Volume 15, Issue 2, 1988
  • J.L. Humm, A microdosimetric model of astatine-211 labeled antibodies for radioimmunotherapy, International Journal of Radiation Oncology*Biology*Physics, Volume 13, Issue 11, November 1987
  • I. Brown, Astatine-211: Its possible applications in cancer therapy, International Journal of Radiation Applications and Instrumentation. Part A. Applied Radiation and Isotopes, Volume 37, Issue 8, 1986