Isotopes of astatine

Isotopes of astatine  (₈₅At)

Main isotopes [1] Decay abun­dance half-life (t1/2) mode pro­duct 207At synth 1.81 h β+ 90% 207Po α 10% 203Bi 208At synth 1.63 h β+99.5% 208Po α0.55% 204Bi 209At synth 5.41 h β+96.1% 209Po α3.9% 205Bi 210At synth 8.1 h β+99.8% 210Po α0.175% 206Bi 211At synth 7.214 h ε 58.2% 211Po α41.8% 207Bi

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Astatine (₈₅At) has 41 known isotopes, all of which are radioactive; their mass numbers range from 188 to 229 (though ¹⁸⁹At is undiscovered). There are also 24 known metastable excited states. The longest-lived isotope is ²¹⁰At, which has a half-life of 8.1 hours; the longest-lived isotope existing in naturally occurring decay chains is ²¹⁹At with a half-life of 56 seconds.

List of isotopes

Nuclide [n 1]	Z	N	Isotopic mass (Da) [2] [n 2] [n 3]	Half-life [1]	Decay mode [1] [n 4]	Daughter isotope [n 5]	Spin and parity [1] [n 6] [n 7]	Isotopic abundance
	Excitation energy [n 7]
188At [3]	85	103		190+350 −80 μs	α (~50%)	184Bi
					p (~50%)	187Po
190At [4]	85	105		1.0+1.4 −0.4 ms	α	186Bi	(10−)
191At	85	106	191.004148(17)	2.1(8) ms	α	187Bi	1/2+
191mAt	58(20) keV			2.2(4) ms	α	187Bi	(7/2−)
192At	85	107	192.003141(3)	11.5(6) ms	α	188Bi	3+#
192mAt [n 8]	0(40) keV			88(6) ms	α	188mBi	(9−, 10−)
193At	85	108	192.999928(23)	29(5) ms	α	189Bi	1/2+
193m1At [n 8]	8(9) keV			21(5) ms	α	189m1Bi	7/2−
193m2At	42(9) keV			28(4) ms	IT (76%)	193At	13/2+
					α (24%)	189m2Bi
194At	85	109	193.999231(25)	286(7) ms	α (91.7%#)	190Bi	(5−)
					β+ (8.3%#)	194Po
					β+, SF (0.032%#)	(various)
194mAt [n 8]	−20(40) keV			323(7) ms	α (91.7%#)	190Bi	10−
					β+ (8.3%#)	194Po
					β+, SF (0.032%#)	(various)
195At	85	110	194.996274(10)	290(20) ms	α	191mBi	1/2+
					β+ ?	195Po
195mAt	29(7) keV			143(3) ms	α (88%)	191Bi	7/2-
					IT (12%)	195At
					β+?	195Po
196At	85	111	195.99580(3)	377(4) ms	α (97.5%)	192Bi	(3+)
					β+ (2.5%)	196Po
					β+, SF (0.009%)	(various)
196m1At [n 8]	−40(40) keV			20# ms	α	192mBi	10−#
196m2At	157.9(1) keV			11(2) μs	IT	196At	(5+)
197At	85	112	196.993177(9)	388.2(56) ms	α (96.1%)	193Bi	9/2−
					β+ (3.9%)	197Po
197m1At	45(8) keV			2.0(2) s	α	193m1Bi	1/2+
					IT (<0.004%)	197At
					β+?	197Po
197m2At	310.7(2) keV			1.3(2) μs	IT	197At	13/2+
198At	85	113	197.992798(5)	4.47(5) s	α (97%)	194Bi	3+
					β+ (3%)	198Po
198mAt	266.6(27) keV			1.23(5) s	α (93%)		10−
					β+ ?	198Po
					IT ?	198Po
199At	85	114	198.990528(6)	7.02(12) s	α (89%)	195Bi	9/2−
					β+ (11%)	199Po
199m1At	244.0(10) keV			273(9) ms	IT (99%)		1/2+
					α (1%)	195Bi
199m2At	572.9(1) keV			70(20) ns	IT		13/2+
199m3At	2293.4(5) keV			800(50) ns	IT		(29/2+)
200At	85	115	199.990351(26)	43.2(9) s	α (52%)	196Bi	(3+)
					β+ (48%)	200Po
200m1At	112.9(29) keV			47(1) s	β+ (57%)	200Po	(7+)
					α (43%)	196Bi
					IT ?	200At
200m2At	343.8(30) keV			8.0(21) s	IT ?	200At	(10−)
					α (10.5%)	196Bi
					β+ ?	200Po
201At	85	116	200.988417(9)	85.2(16) s	α (71%)	197Bi	9/2−
					β+ (29%)	201Po
201m1At	459(1) keV			45(3) ms	IT		1/2+
201m2At	459(1) keV			3.39(9) μs	IT		29/2+
202At	85	117	201.988626(30)	184(1) s	β+ (88%)	202Po	3+
					α (12%)	198Bi
202m1At	190(40) keV			182(2) s	β+ (91.5%)	202Po	7+
				α (8.5%)	198Bi
				IT ?	202At
202m2At	590(40) keV			460(50) ms	IT (99.904%)	202At	10−
					α (0.096%)	198Bi
					IT ?	202At
203At	85	118	202.986943(11)	7.4(2) min	β+ (69%)	203Po	9/2−
					α (31%)	199Bi
203m1At	683.4(3) keV			3.5(6) ms	IT		1/2+
203m2At	2330.1(4) keV			9.77(21) μs	IT		29/2+
204At	85	119	203.987251(24)	9.12(11) min	β+ (96.2%)	204Po	7+
					α (3.8%)	200Bi
204mAt	587.30(20) keV			108(10) ms	IT	204At	10−
205At	85	120	204.986061(13)	26.9(8) min	β+ (90%)	205Po	9/2−
					α (10%)	201Bi
205mAt	2339.64(23) keV			7.76(14) μs	IT	205At	29/2+
206At	85	121	205.986646(15)	30.6(8) min	β+ (99.1%)	206Po	(6)+
					α (0.9%)	202Bi
206mAt	810(2) keV			813(21) ns	IT	206At	(10)−
207At	85	122	206.985800(13)	1.81(3) h	β+ (~90%)	207Po	9/2−
					α (~10%)	203Bi
207mAt	2117.3(6) keV			108(2) ns	IT	207At	25/2+
208At	85	123	207.986613(10)	1.63(3) h	β+ (99.45%)	208Po	6+
					α (0.55%)	204Bi
208mAt	2276.4(18) keV			1.5(2) μs	IT	208At	16-
209At	85	124	208.986169(5)	5.41(5) h	β+ (96.1%)	209Po	9/2−
					α (3.9%)	205Bi
209mAt	2429.32(22) keV			916(10) ns	IT	209At	29/2+
210At	85	125	209.987147(8)	8.1(4) h	β+ (99.825%)	210Po	(5)+
					α (0.175%)	206Bi
210m1At	2549.6(2) keV			482(6) ns	IT	210At	(15)−
210m2At	4027.7(2) keV			5.66(7) μs	IT	210At	(19)+
211At	85	126	210.9874962(29)	7.214(7) h	EC (58.2%)	211Po	9/2−
					α (41.8%)	207Bi
211mAt	4814.5(5) keV			4.23(7) μs	IT	211At	(39/2-)
212At	85	127	211.9907373(26)	314(3) ms	α [n 9]	208Bi	(1−)
212m1At	222.9(9) keV			119(3) ms	α	208Bi	(9−)
212m2At	4771.4(15) keV			152(5) μs	IT	212At	(25−)
213At	85	128	212.992937(5)	125(6) ns	α [n 10]	209Bi	9/2−
213m1At	1358(23) keV			110(17) ns	IT	213At	25/2-#
213m2At	2998(27) keV			45(4) μs	IT	213At	49/2+#
214At	85	129	213.996372(4)	558(10) ns	α	210Bi	1−
214m1At	59(9) keV			265(30) ns	α	210Bi
214m2At	232(5) keV			760(15) ns	α	210mBi [7]	9−
215At	85	130	214.998651(7)	37(3) μs	α	211Bi	9/2−	Trace [n 11]
216At	85	131	216.002423(4)	300(30) μs	α [n 12]	212Bi	1−
216mAt	161(11) keV			100# μs	α	212m1Bi [9]	9−#
217At	85	132	217.004718(5)	32.6(3) ms	α (99.992%)	213Bi	9/2−	Trace [n 13]
					β− (0.008%)	217Rn
218At	85	133	218.008696(12)	1.28(6) s	α (~100%)	214Bi	(2−,3−)	Trace [n 14]
					β− (?)	218Rn
219At	85	134	219.011161(3)	56(3) s	α (93.6%)	215Bi	(9/2−)	Trace [n 11]
					β− (6.4%)	219Rn
220At	85	135	220.015433(15)	3.71(4) min	β− (92%)	220Rn	3(−#)
					α (8%)	216Bi
221At	85	136	221.018017(15)	2.3(2) min	β−	221Rn	3/2−#
222At	85	137	222.022494(17)	54(10) s	β−	222Rn
223At	85	138	223.025151(15)	50(7) s	β−	223Rn	3/2−#
224At	85	139	224.029749(24)	2.5 +/- 1.5 min	β−	224Rn	2+#
225At	85	140	225.03253(32)#	3# s (>300 ns)	β− ?	225Rn	1/2+#
226At	85	141	226.03721(32)#	7# min (>300 ns)	β− ?	226Rn	2+#
227At	85	142	227.04018(32)#	5# s (>300 ns)	β− ?	227Rn	1/2+#
228At	85	143	228.04496(43)#	1# min (>300 ns)	β− ?	228Rn	3+#
229At	85	144	229.04819(43)#	1# s (>300 ns)	β− ?	229Rn	1/2+#
This table header & footer: view

1. ^mAt – Excited nuclear isomer.
2. ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
3. # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
4. Modes of decay:

   EC:	Electron capture
   IT:	Isomeric transition

5. Bold italics symbol as daughter – Daughter product is nearly stable.
6. ( ) spin value – Indicates spin with weak assignment arguments.
7. # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
8. Order of ground state and isomer is uncertain.
9. Theoretically capable of β⁺ decay to ²¹²Po or β⁻ decay to ²¹²Rn; the branching ratios are expected to be <3×10⁻²% and <2×10⁻⁶% (partial half-lives >17.4 min and >182 d) respectively. ^[5]
10. Theoretically capable of electron capture to ²¹³Po; the branching ratio is expected to be <2.5×10⁻¹²% (partial half-life >57.9 d). ^[6]
11. Intermediate decay product of ²³⁵U
12. Theoretically capable of electron capture to ²¹⁶Po or β⁻ decay to ²¹⁶Rn; the branching ratios are expected to be <3×10⁻⁷% and <6×10⁻³% (partial half-lives >1.2 d and >5.0 s) respectively. ^[8]
13. Intermediate decay product of ²³⁷Np
14. Intermediate decay product of ²³⁸U

Alpha decay

Alpha decay characteristics for sample astatine isotopes ^[a]

Mass number	Mass excess [10]	Mass excess of daughter [10]	Average energy of alpha decay	Half-life [10]	Probability of alpha decay [10]	Alpha decay half-life
207	−13.243 MeV	−19.116 MeV	5.873 MeV	1.80 h	8.6%	20.9 h
208	−12.491 MeV	−18.243 MeV	5.752 MeV	1.63 h	0.55%	12.3 d
209	−12.880 MeV	−18.638 MeV	5.758 MeV	5.41 h	4.1%	5.5 d
210	−11.972 MeV	−17.604 MeV	5.632 MeV	8.1 h	0.175%	193 d
211	−11.647 MeV	−17.630 MeV	5.983 MeV	7.21 h	41.8%	17.2 h
212	−8.621 MeV	−16.436 MeV	7.825 MeV	0.31 s	≈100%	0.31 s
213	−6.579 MeV	−15.834 MeV	9.255 MeV	125 ns	100%	125 ns
214	−3.380 MeV	−12.366 MeV	8.986 MeV	558 ns	100%	558 ns
219	10.397 MeV	4.073 MeV	6.324 MeV	56 s	97%	58 s
220	14.350 MeV	8.298 MeV	6.052 MeV	3.71 min	8%	46.4 min
221 [b]	16.810 MeV	11.244 MeV	5.566 MeV	2.3 min	experimentally alpha stable	∞

Astatine has 23 nuclear isomers (nuclei with one or more nucleons  – protons or neutrons  – in an excited state). A nuclear isomer may also be called a "meta-state"; this means the system has more internal energy than the "ground state" (the state with the lowest possible internal energy), making the former likely to decay into the latter. There may be more than one isomer for each isotope. The most stable of them is astatine-202m1, ^[c] which has a half-life of about 3 minutes; this is longer than those of all ground states except those of isotopes 203–211 and 220. The least stable one is astatine-214m1; its half-life of 265 ns is shorter than those of all ground states except that of astatine-213. ^[10]

Alpha decay energy follows the same trend as for other heavy elements. ^[11] Lighter astatine isotopes have quite high energies of alpha decay, which become lower as the nuclei become heavier. However, astatine-211 has a significantly higher energy than the previous isotope; it has a nucleus with 126 neutrons, and 126 is a magic number (corresponding to a filled neutron shell). Despite having a similar half-life time as the previous isotope (8.1 hours for astatine-210 and 7.2 hours for astatine-211), the alpha decay probability is much higher for the latter: 41.8 percent versus just 0.18 percent. ^{[10] [d]} The two following isotopes release even more energy, with astatine-213 releasing the highest amount of energy of all astatine isotopes. For this reason, it is the shortest-lived astatine isotope. ^[11] Even though heavier astatine isotopes release less energy, no long-lived astatine isotope exists; this happens due to the increasing role of beta decay. ^[11] This decay mode is especially important for astatine: as early as 1950, it was postulated that the element has no beta-stable isotopes (i.e. ones that do not undergo beta decay at all), ^[12] though nuclear mass measurements reveal that ²¹⁵At is in fact beta-stable, as it has the lowest mass of all isobars with A = 215. ^[13] A beta decay mode has been found for all other astatine isotopes except for ^212-216At and their isomers. ^{[10] [1]} Among other isotopes: astatine-210 and the lighter isotopes decay by positron emission; astatine-217 and the heavier isotopes undergo beta decay; and astatine-211 decays by electron capture instead. ^[10] Astatine-212 and astatine-216 are expected to decay either way.

The most stable isotope of astatine is astatine-210, which has a half-life of about 8.1 hours. This isotope's primary decay mode is positron emission to the relatively long-lived alpha emitter, polonium-210. In total, only five isotopes of astatine have half-lives exceeding one hour: those between 207 and 211. The least stable ground state isotope is astatine-213, with a half-life of about 125 nanoseconds. It undergoes alpha decay to the extremely long-lived (in practice, stable) isotope bismuth-209. ^[10]

See also

Daughter products other than astatine

• Isotopes of radon
• Isotopes of polonium
• Isotopes of bismuth

Notes

1. In the table, under the words "mass excess", the energy equivalents are given rather than the real mass excesses; "mass excess daughter" stands for the energy equivalent of the mass excess sum of the daughter of the isotope and the alpha particle; "alpha decay half-life" refers to the half-life if decay modes other than alpha are omitted.
2. Since astatine-221 has not been shown to undergo alpha decay, the alpha decay energy is theoretical. The value for mass excess is calculated rather than measured.
3. "m1" means that this state of the isotope is the next possible one above – energy greater than – the ground state. "m2" and similar designations refer to further higher energy states. The number may be dropped if there is only one well-established meta state, such as astatine-216m. Note that other designation techniques exist.
4. This means that if decay modes other than alpha are omitted, then astatine-210 has an alpha half-life of 4,628.6 hours (128.9 days) and astatine-211 has one of 17.2 hours (0.9 days). Therefore, astatine-211 is less stable toward alpha decay than the lighter isotope, and is more likely to undergo alpha decay in the same time period.

References

1. Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
2. Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C. 45 (3): 030003. doi:10.1088/1674-1137/abddaf.
3. Kokkonen, Henna; Auranen, Kalle; Siwach, Pooja; Arumugam, Paramasivan; Briscoe, Andrew D.; Eeckhaudt, Sarah; Ferreira, Lidia S.; Grahn, Tuomas; Greenlees, Paul T.; Jones, Pete; Julin, Rauno; Juutinen, Sakari; Leino, Matti; Leppänen, Ari-Pekka; Maglione, Enrico; Nyman, Markus; Page, Robert D.; Pakarinen, Janne; Rahkila, Panu; Sarén, Jan; Scholey, Catherine; Sorri, Juha; Uusitalo, Juha; Venhart, Martin (29 May 2025). "New proton emitter 188At implies an interaction unprecedented in heavy nuclei". Nature Communications. 16 (1). doi:10.1038/s41467-025-60259-6.
4. Kokkonen, H.; Auranen, K.; Uusitalo, J.; Eeckhaudt, S.; Grahn, T.; Greenlees, P. T.; Jones, P.; Julin, R.; Juutinen, S.; Leino, M.; Leppänen, A.-P.; Nyman, M.; Pakarinen, J.; Rahkila, P.; Sarén, J.; Scholey, C.; Sorri, J.; Venhart, M. (20 June 2023). "Properties of the new α -decaying isotope At 190". Physical Review C. 107 (6). doi:10.1103/PhysRevC.107.064312.
5. "Adopted Levels for ²¹²At" (PDF). NNDC Chart of Nuclides.
6. "Adopted Levels for ²¹³At" (PDF). NNDC Chart of Nuclides.
7. "²¹⁴At α decay (760 ns)" (PDF). NNDC Chart of Nuclides.
8. "Adopted Levels for ²¹⁶At" (PDF). NNDC Chart of Nuclides.
9. "²¹⁶At α decay: J=9" (PDF). NNDC Chart of Nuclides.
10. Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
11. Lavrukhina & Pozdnyakov 1966, p. 232.
12. Rankama, Kalervo (1956). Isotope geology (2nd ed.). Pergamon Press. p. 403. ISBN   978-0-470-70800-2.
13. Audi, G.; Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S. (2017). "The NUBASE2016 evaluation of nuclear properties" (PDF). Chinese Physics C. 41 (3): 030001. Bibcode:2017ChPhC..41c0001A. doi:10.1088/1674-1137/41/3/030001.

• Lavrukhina, Avgusta Konstantinovna; Pozdnyakov, Aleksandr Aleksandrovich (1966). Аналитическая химия технеция, прометия, астатина и франция[Analytical Chemistry of Technetium, Promethium, Astatine, and Francium] (in Russian). Nauka.
• Isotope masses from:
  • Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
• Half-life, spin, and isomer data selected from the following sources.
  • Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
  • National Nuclear Data Center. "NuDat 3.0 database". Brookhaven National Laboratory.

• • Holden, Norman E. (2004). "11. Table of the Isotopes". In Lide, David R. (ed.). CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. ISBN   978-0-8493-0485-9.