Astatine (At)

Astatine is a radioactive chemical element with an atomic number 85 in the periodic table of elements. The total amount of astatine found naturally in the Earth’s crust is almost 25 grams at any given time, which makes astatine the rarest chemical element on Earth. Being a member of the family of halogen elements in the periodic table, the outer shell of astatine comprises seven valence electrons.

Fact Box

Chemical and Physical Properties of Astatine

The symbol in the periodic table of elements: 

Atomic number: 85

Atomic weight (mass): 209.9871 [210 – average]

Group number: 17

Period: 6

Color: A shiny dark-colored chemical element

Physical state: Solid metal at room temperature


Electronegativity according to Pauling: 2.2

Density: No data available

Melting point: 302°C

Boiling point: 337°C (estimation)

Van der Waals radius: 200 pm

Ionic radius: 


Most characteristic isotopes: 210At, 211At

Electronic shell: 

The energy of the first ionization: 

The energy of the second ionization: 

Discovery date: In 1940 by D.R.Corson, K.R. MacKenzie, E.Segré.

With the periodic table symbol At, the atomic mass of 209.9871 g.mol -1, and electronic configuration [Xe] 4f145d106s26p5, аstatine reaches its (estimated) boiling point at 337°C with probable valences of 1, 3, 5, or 7, while the melting point is achieved at 302°C. Both melting and boiling points of astatine increase with the atomic number. This member of the halogen family of elements in the periodic table has an electronegativity of 2.2, according to Pauling, whereas the atomic radius according to van der Waals is 200 pm.

The chemical properties of astatine also include:

  • plating of astatine onto a cathode;
  • forming a stable monatomic cation in aqueous solution;
  • co-precipitating of astatine with metal sulfides in hydrochloric acid.

How Was Astatine Discovered?

The story of astatine begins in 1869 when the Russian chemist Dmitri Mendeleev managed to determine the properties of a chemical element with an atomic number 85 that was yet to be named. The first choice for the name of the radioactive metal was eka-iodine, due to the fact that it was placed under iodine (I) – a member of the halogen family of elements in the periodic table.

The Romanian physicist Horia Hulubei and the French physicist Yvette Cauchois believed that they had discovered element 85 via X-ray analysis. Their efforts were disregarded by the Austrian chemist Friedrich Paneth in 1947. 

However, in 1939, there was information that this particular element was independently discovered by the Alabama Polytechnic Institute researcher, Fred Allison, who opted for the name “alabamine” in an attempt to label the newly discovered chemical element. Unfortunately, due to his dysfunctional equipment, the resulting formulae could not be used by the other researchers. In the meantime, World War II disrupted any further research on the heaviest halogen element in the periodic table. 

In 1940, three researchers at the University of California, Berkeley (Dale R. Corson, Kenneth Ross Mackenzie, and Emilio Segrè) managed to resume the research and artificially produce astatine by bombarding bismuth-209 with alpha particles in a cyclotron particle accelerator, since this highly radioactive and unstable element could not be found in nature. Astatine-211 and two free neutrons were produced as a result of this chemical reaction triggered by the aforementioned University of California researchers. 

How Did Astatine Get Its Name?

The name of this radioactive chemical element comes from the Greek word “astatos” (“αστατος”). This Greek word carries the meaning of ‘unstable’ which resembles the nature of astatine. The chemical properties of astatine were defined by the scientists from the Jefferson Laboratory.

Where Can You Find Astatine?

Astatine is a man-made chemical element, i.e. it cannot be found abundantly in nature. This radioactive metal is produced by bombarding a bismuth target (bismuth-209 isotope) with alpha particles producing At-209, At-210, and At-211. 

This radioactive chemical element with the highest weight among the halogen elements can be also traced in the following radioactive decay series: natural astatine-218 in the uranium series, astatine-216 in the thorium series, and astatine-215 as well as astatine-219 in the actinium series. 

Astatine in Everyday Life

The Use of Astatine in Nuclear Medicine

This artificially radioactive element is applied in medicine as a radioisotope for the treatment of malignant tumors and cancer. The widespread use of astatine is due to the astatine-211 isotope. Namely, it’s applied for targeted alpha-particle therapy (radiotherapy).

How Dangerous Is Astatine?

The extremely small amount of At-215, At-218, and At-219 that can be traced in nature results from the decay of uranium and thorium. Since astatine is not naturally found in significant amounts and has a very short half-life of 8.1 hours or less, it does not present a significant health hazard. However, this man-made radioactive element can display the negative side of its radioactive properties if handled without care in the research labs or medical institutes. High exposure to astatine can lead to astatine bioaccumulation in the thyroid gland.

Astatine Isotopes 

Astatine does not have any natural isotopes. The list of known isotopes contains 39 radioactive isotopes, with mass numbers from 191 to 229. According to the Jefferson Laboratory, the number of the longest-lived isotope among them is astatine-210 (210At). At the same time, this is also the most stable isotope of this radioactive element of the periodic table.

The following is a tabular representation of astatine isotopes:


[n 1]

Z N Isotopic mass (Da)

[n 2][n 3]

Half-life Decay


[n 4]



Spin and


[n 5][n 6]



Excitation energy[n 6]
191At 85 106 1.7(+11−5) ms (1/2+)
191mAt 2.1(+4−3) ms (7/2−)
192At 85 107 192.00314(28) 11.5(0.6) ms α (99.79%) 188Bi 3+#
β+, SF (0.21%) (various)
192mAt 330(90)# keV 88(6) ms α (99.79%) 188mBi (9-, 10−)
β+, SF (0.21%) (various)
193At 85 108 192.99984(6) 28(+5−4) ms α 189Bi (1/2+)
193m1At 50 keV 21(5) ms (7/2−)
193m2At 39 keV 27(+4−5) ms (13/2+)
194At 85 109 193.99873(20) 286(7) ms α 190Bi (4-, 5-)
β+ (rare) 194Po
194mAt 480(190) keV 323(7) ms α 190Bi (9-, 10-)
IT (rare) 194At
195At 85 110 194.996268(10) 328(20) ms α (75%) 191Bi (1/2+)
β+ (25%) 195Po
195mAt 34(7) keV 147(5) ms (7/2-)
196At 85 111 195.99579(6) 253(9) ms α (96%) 192Bi (3+)
β+ (4.0%) 196Po
196m1At −30(80) keV 20# ms (10−)
196m2At 157.9(1) keV 11 µs (5+)
197At 85 112 196.99319(5) 0.390(16) s α (96%) 193Bi (9/2−)
β+ (4.0%) 197Po
197mAt 52(10) keV 2.0(2) s (1/2+)
198At 85 113 197.99284(5) 4.2(3) s α (94%) 194Bi (3+)
β+ (6%) 198Po
198mAt 330(90)# keV 1.0(2) s (10−)
199At 85 114 198.99053(5) 6.92(13) s α (89%) 195Bi (9/2−)
β+ (11%) 199Po
200At 85 115 199.990351(26) 43.2(9) s α (57%) 196Bi (3+)
β+ (43%) 200Po
200m1At 112.7(30) keV 47(1) s α (43%) 196Bi (7+)
IT 200At
β+ 200Po
200m2At 344(3) keV 3.5(2) s (10−)
201At 85 116 200.988417(9) 85(3) s α (71%) 197Bi (9/2−)
β+ (29%) 201Po
202At 85 117 201.98863(3) 184(1) s β+ (88%) 202Po (2, 3)+
α (12%) 198Bi
202m1At 190(40) keV 182(2) s (7+)
202m2At 580(40) keV 460(50) ms (10−)
203At 85 118 202.986942(13) 7.37(13) min β+ (69%) 203Po 9/2−
α (31%) 199Bi
204At 85 119 203.987251(26) 9.2(2) min β+ (96%) 204Po 7+
α (3.8%) 200Bi
204mAt 587.30(20) keV 108(10) ms IT 204At (10−)
205At 85 120 204.986074(16) 26.2(5) min β+ (90%) 205Po 9/2−
α (10%) 201Bi
205mAt 2339.65(23) keV 7.76(14) µs 29/2+
206At 85 121 205.986667(22) 30.6(13) min β+ (99.11%) 206Po (5)+
α (0.9%) 202Bi
206mAt 807(3) keV 410(80) ns (10)−
207At 85 122 206.985784(23) 1.80(4) h β+ (91%) 207Po 9/2−
α (8.6%) 203Bi
208At 85 123 207.986590(28) 1.63(3) h β+ (99.5%) 208Po 6+
α (0.55%) 204Bi
209At 85 124 208.986173(8) 5.41(5) h β+ (96%) 209Po 9/2−
α (4.0%) 205Bi
210At 85 125 209.987148(8) 8.1(4) h β+ (99.8%) 210Po (5)+
α (0.18%) 206Bi
210m1At 2549.6(2) keV 482(6) µs (15)−
210m2At 4027.7(2) keV 5.66(7) µs (19)+
211At 85 126 210.9874963(30) 7.214(7) h EC (58.2%) 211Po 9/2−
α (42%) 207Bi
212At 85 127 211.990745(8) 0.314(2) s α (99.95%) 208Bi (1−)
β+ (0.05%) 212Po
β (2×10−6%) 212Rn
212m1At 223(7) keV 0.119(3) s α (99%) 208Bi (9−)
IT (1%) 212At
212m2At 4771.6(11) keV 152(5) µs (25−)
213At 85 128 212.992937(5) 125(6) ns α 209Bi 9/2−
214At 85 129 213.996372(5) 558(10) ns α 210Bi 1−
214m1At 59(9) keV 265(30) ns
214m2At 231(6) keV 760(15) ns 9−
215At 85 130 214.998653(7) 0.10(2) ms α 211Bi 9/2− Trace[n 7]
216At 85 131 216.002423(4) 0.30(3) ms α (99.99%) 212Bi 1−
β (.006%) 216Rn
EC (3×10−7%) 216Po
216mAt 413(5) keV 100# µs (9−)
217At 85 132 217.004719(5) 32.3(4) ms α (99.98%) 213Bi 9/2− Trace[n 8]
β (.012%) 217Rn
218At 85 133 218.008694(12) 1.5(3) s α (99.9%) 214Bi 1−# Trace[n 9]
β (0.10%) 218Rn
219At 85 134 219.011162(4) 56(3) s α (97%) 215Bi (9/2-) Trace[n 7]
β (3.0%) 219Rn
220At 85 135 220.01541(6) 3.71(4) min β (92%) 220Rn 3(−#)
α (8.0%) 216Bi
221At 85 136 221.01805(21)# 2.3(2) min β 221Rn 3/2−#
222At 85 137 222.02233(32)# 54(10) s β 222Rn
223At 85 138 223.02519(43)# 50(7) s β 223Rn 3/2−#
224At 85 139 224.02975(22)# 2.5(1.5) min β 224Rn

Source: Wikipedia

Alpha Decay of Astatine Isotopes

The short half-life of astatine makes this highly radioactive chemical element decay into bismuth, radon, polonium, or other isotopes of astatine. When the mass of the astatine nucleus increases, the high energies of alpha decay decrease, and vice versa. 

The most stable astatine isotope (210At) decays into bismuth-206 through alpha decay or into polonium-210 through electron capture to polonium-211, which undergoes further alpha decay in the form of an extremely short-lived nuclide. 

Alpha decay characteristics for sample astatine isotopes[h]




Half-life[8] Probability

of alpha





207 −13.243 MeV 1.80 h 8.6% 20.9 h
208 −12.491 MeV 1.63 h 0.55% 12.3 d
209 −12.880 MeV 5.41 h 4.1% 5.5 d
210 −11.972 MeV 8.1 h 0.175% 193 d
211 −11.647 MeV 7.21 h 41.8% 17.2 h
212 −8.621 MeV 0.31 s ≈100% 0.31 s
213 −6.579 MeV 125 ns 100% 125 ns
214 −3.380 MeV 558 ns 100% 558 ns
219 10.397 MeV 56 s 97% 58 s
220 14.350 MeV 3.71 min 8% 46.4 min
221[i] 16.810 MeV 2.3 min experimentally

alpha stable

Source: Wikipedia

Astatine Compounds 

Astatine forms compounds with the following elements or groups of elements: oxygen, sulfur, halides, selenium, palladium, nitrogen, lead, sodium, silver, and boron. Oxidation states of astatine range from −1 to +7 and are typically expressed with an odd number. 

Hydrogen astatide (HAt) is created by a reaction of astatine with hydrogen, i.e. a weaker form of hydrochloric acid. The molecule of this compound is made of an astatine atom that forms two chemical bonds to a hydrogen atom. In this way, it becomes a hydrogen halide. 

Astatides of silver, sodium, lead, palladium, and thallium, comprise some of the rare metal compounds of astatine. 

The following is a list of some of the astatine compounds:

  • Astatobenzene, C6H5At
  • Hypochlorite, C6H5AtO2
  • Astatine nitrate, [At(C5H5N)2]NO3

5 Interesting Facts and Explanations

  1. Dmitry Ivanovich Mendeleyev (January 27, 1834 – February 2, 1907) is the Russian chemist who created the periodic table of elements according to their similarity in electron configurations, as well as their chemical and physical properties. 
  2. Hydrogen astatide (HAt) is also labeled as astatine hydride astatine, astido hydrogen or hydroastatic acid. 
  3. The chemical element astatine has the strongest metallic properties among the other chemical elements from the halogen family in the periodic table. 
  4. Astatine is concentrated in the thyroid gland of animals, just like iodine. In humans, it’s mainly concentrated in the lungs, spleen, and liver. 
  5. The halogen family of elements consists of the following chemical elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), and tennessine (Ts).

Chemical Property and physical property of element Astatine

Symbol of Astatine: At
Name: Astatine
Atomic Number of Astatine: 85
Group of Astatine: Halogen
Crystal Structure of Astatine: Unknown
Atomic Weight of Astatine: -209.9871
Shells of Astatine: 2,8,18,32,18,7
Orbitals of Astatine: [Xe] 4f14 5d10 6s2 6p5
Valence of Astatine: 1,3,5,7
Melting Point of Astatine:
Boiling Point of Astatine:
Electro Negativity of Astatine: 2.2
Covalent Radius of Astatine: 1.45 Å
Ionic Radius of Astatine:
Atomic Radius of Astatine: 1.43 Å
Atomic Volume of Astatine:
Name Origin of Astatine: Greek: astatos (unstable).
Discovered of Astatine By: D.R.Corson, K.R.MacKenzie, E.Segré
Year: 1940
Location: United States
Pronounced of Astatine: AS-teh-teen
Oxydation States of Astatine: (±1),3,5,7
Density of Astatine:
Uses of Astatine: Since its isotopes have such short half-lives there are no commercially significant compounds of astatine.
Description of Astatine: Colorless, odorless, tasteless, radioactive, heavy, noble gas.