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.

Chemical and Physical Properties of Astatine

Atomic number85
GroupHalogen (Group 17)
Crystal StructureUnknown
Atomic weight (mass)209.9871 [210 – average]
Orbitals[Xe] 4f14 5d10 6s2 6p5
ColorA shiny dark-colored chemical element
Physical stateSolid metal at room temperature
Half-lifeFrom less than 0.90(25) milliseconds to 58 minutes
Electronegativity according to Pauling2.2
Covalent Radius1.45 Å
Atomic Radius1.43 Å
Ionic Radius
Van der Waals radius200 pm
Melting point302°C
Boiling point337°C (estimation)
DensityNo data available
Name OriginGreek: astatos (unstable)
Discovery ByD.R.Corson, K.R.MacKenzie, E.Segré
LocationUnited States
Oxidation States(±1),3,5,7
UsesSince its isotopes have such short half-lives there are no commercially significant compounds of astatine.
DescriptionColorless, odorless, tasteless, radioactive, heavy, noble gas.

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]

ZNIsotopic mass (Da)

[n 2][n 3]



[n 4]



Spin and


[n 5][n 6]



Excitation energy[n 6]
191At85106 1.7(+11−5) ms  (1/2+) 
191mAt 2.1(+4−3) ms  (7/2−) 
192At85107192.00314(28)11.5(0.6) msα (99.79%)188Bi3+# 
β+, SF (0.21%)(various)
192mAt330(90)# keV88(6) msα (99.79%)188mBi(9-, 10−) 
β+, SF (0.21%)(various)
193At85108192.99984(6)28(+5−4) msα189Bi(1/2+) 
193m1At50 keV21(5) ms  (7/2−) 
193m2At39 keV27(+4−5) ms  (13/2+) 
194At85109193.99873(20)286(7) msα190Bi(4-, 5-) 
β+ (rare)194Po
194mAt480(190) keV323(7) msα190Bi(9-, 10-) 
IT (rare)194At
195At85110194.996268(10)328(20) msα (75%)191Bi(1/2+) 
β+ (25%)195Po
195mAt34(7) keV147(5) ms  (7/2-) 
196At85111195.99579(6)253(9) msα (96%)192Bi(3+) 
β+ (4.0%)196Po
196m1At−30(80) keV20# ms  (10−) 
196m2At157.9(1) keV11 µs  (5+) 
197At85112196.99319(5)0.390(16) sα (96%)193Bi(9/2−) 
β+ (4.0%)197Po
197mAt52(10) keV2.0(2) s  (1/2+) 
198At85113197.99284(5)4.2(3) sα (94%)194Bi(3+) 
β+ (6%)198Po
198mAt330(90)# keV1.0(2) s  (10−) 
199At85114198.99053(5)6.92(13) sα (89%)195Bi(9/2−) 
β+ (11%)199Po
200At85115199.990351(26)43.2(9) sα (57%)196Bi(3+) 
β+ (43%)200Po
200m1At112.7(30) keV47(1) sα (43%)196Bi(7+) 
200m2At344(3) keV3.5(2) s  (10−) 
201At85116200.988417(9)85(3) sα (71%)197Bi(9/2−) 
β+ (29%)201Po
202At85117201.98863(3)184(1) sβ+ (88%)202Po(2, 3)+ 
α (12%)198Bi
202m1At190(40) keV182(2) s  (7+) 
202m2At580(40) keV460(50) ms  (10−) 
203At85118202.986942(13)7.37(13) minβ+ (69%)203Po9/2− 
α (31%)199Bi
204At85119203.987251(26)9.2(2) minβ+ (96%)204Po7+ 
α (3.8%)200Bi
204mAt587.30(20) keV108(10) msIT204At(10−) 
205At85120204.986074(16)26.2(5) minβ+ (90%)205Po9/2− 
α (10%)201Bi
205mAt2339.65(23) keV7.76(14) µs  29/2+ 
206At85121205.986667(22)30.6(13) minβ+ (99.11%)206Po(5)+ 
α (0.9%)202Bi
206mAt807(3) keV410(80) ns  (10)− 
207At85122206.985784(23)1.80(4) hβ+ (91%)207Po9/2− 
α (8.6%)203Bi
208At85123207.986590(28)1.63(3) hβ+ (99.5%)208Po6+ 
α (0.55%)204Bi
209At85124208.986173(8)5.41(5) hβ+ (96%)209Po9/2− 
α (4.0%)205Bi
210At85125209.987148(8)8.1(4) hβ+ (99.8%)210Po(5)+ 
α (0.18%)206Bi
210m1At2549.6(2) keV482(6) µs  (15)− 
210m2At4027.7(2) keV5.66(7) µs  (19)+ 
211At85126210.9874963(30)7.214(7) hEC (58.2%)211Po9/2− 
α (42%)207Bi
212At85127211.990745(8)0.314(2) sα (99.95%)208Bi(1−) 
β+ (0.05%)212Po
β (2×10−6%)212Rn
212m1At223(7) keV0.119(3) sα (99%)208Bi(9−) 
IT (1%)212At
212m2At4771.6(11) keV152(5) µs  (25−) 
213At85128212.992937(5)125(6) nsα209Bi9/2− 
214At85129213.996372(5)558(10) nsα210Bi1− 
214m1At59(9) keV265(30) ns    
214m2At231(6) keV760(15) ns  9− 
215At85130214.998653(7)0.10(2) msα211Bi9/2−Trace[n 7]
216At85131216.002423(4)0.30(3) msα (99.99%)212Bi1− 
β (.006%)216Rn
EC (3×10−7%)216Po
216mAt413(5) keV100# µs  (9−) 
217At85132217.004719(5)32.3(4) msα (99.98%)213Bi9/2−Trace[n 8]
β (.012%)217Rn
218At85133218.008694(12)1.5(3) sα (99.9%)214Bi1−#Trace[n 9]
β (0.10%)218Rn
219At85134219.011162(4)56(3) sα (97%)215Bi(9/2-)Trace[n 7]
β (3.0%)219Rn
220At85135220.01541(6)3.71(4) minβ (92%)220Rn3(−#) 
α (8.0%)216Bi
221At85136221.01805(21)#2.3(2) minβ221Rn3/2−# 
222At85137222.02233(32)#54(10) sβ222Rn  
223At85138223.02519(43)#50(7) sβ223Rn3/2−# 
224At85139224.02975(22)#2.5(1.5) minβ224Rn  

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]





of alpha





207−13.243 MeV1.80 h8.6%20.9 h  
208−12.491 MeV1.63 h0.55%12.3 d  
209−12.880 MeV5.41 h4.1%5.5 d  
210−11.972 MeV8.1 h0.175%193 d  
211−11.647 MeV7.21 h41.8%17.2 h  
212−8.621 MeV0.31 s≈100%0.31 s  
213−6.579 MeV125 ns100%125 ns  
214−3.380 MeV558 ns100%558 ns  
21910.397 MeV56 s97%58 s  
22014.350 MeV3.71 min8%46.4 min  
221[i]16.810 MeV2.3 minexperimentally

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).