Isotopes of astatine

Isotopes of astatine (₈₅At)
α	205Bi
α	206Bi
α	207Bi
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Astatine (₈₅At) has 37 known isotopes, all of which are radioactive; the range of their mass numbers is from 191 to 229. There also exist 23 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.

There are 32 known isotopes of astatine, with atomic masses (mass numbers) of 191 and 193–223.^[2] No stable or even long-lived astatine isotope is known, and no such isotope is expected to exist.^[3]

Alpha decay

Template:Astatine decay characteristics 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,^[a] 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.^[2]

Alpha decay energy follows the same trend as for other heavy elements.^[3] 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.^[2]^[b]^{[clarification needed]} 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.^[3] Even though heavier astatine isotopes release less energy, no long-lived astatine isotope exists; this happens due to the increasing role of beta decay.^[3] 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).^[4] A beta decay mode has been found for all astatine isotopes except for astatine-213, astatine-214, astatine-215, and astatine-216m.^[2] Among other isotopes: astatine-210 and the lighter isotopes decay by positron emission); astatine-216 and the heavier isotopes undergo beta decay; astatine-212 decays via either ways; and astatine-211 decays by electron capture instead.^[2]

The most stable isotope of astatine is At-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 isotope (in practice, a stable one) bismuth-209.^[2]

List of isotopes

nuclide symbol	Z(p)	N(n)	isotopic mass (u)	half-life	decay mode(s)^[5]^{[n 1]}	daughter isotope(s)	nuclear spin	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)
nuclide symbol	excitation energy			half-life	decay mode(s)^[5]^{[n 1]}	daughter isotope(s)	nuclear spin	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)
¹⁹¹At	85	106		1.7(+11−5) ms			(1/2+)
^191mAt				2.1(+4−3) ms			(7/2−)
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)	~40 ms	α	¹⁹⁰Bi	3+#
¹⁹⁴At	85	109	193.99873(20)	~40 ms	β⁺ (rare)	¹⁹⁴Po	3+#
^194mAt	480(190) keV			~250 ms	α	¹⁹⁰Bi	10−#
^194mAt	480(190) keV			~250 ms	IT (rare)	¹⁹⁴At	10−#
¹⁹⁵At	85	110	194.996268(10)	328(20) ms	α (75%)	¹⁹¹Bi	(1/2+)
¹⁹⁵At	85	110	194.996268(10)	328(20) ms	β⁺ (25%)	¹⁹⁵Po	(1/2+)
^195mAt	34(7) keV			147(5) ms			9/2−#
¹⁹⁶At	85	111	195.99579(6)	253(9) ms	α (96%)	¹⁹²Bi	3+#
¹⁹⁶At	85	111	195.99579(6)	253(9) ms	β⁺ (4.0%)	¹⁹⁶Po	3+#
^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−)
¹⁹⁷At	85	112	196.99319(5)	0.390(16) s	β⁺ (4.0%)	¹⁹⁷Po	(9/2−)
^197mAt	52(10) keV			2.0(2) s			(1/2+)
¹⁹⁸At	85	113	197.99284(5)	4.2(3) s	α (94%)	¹⁹⁴Bi	(3+)
¹⁹⁸At	85	113	197.99284(5)	4.2(3) s	β⁺ (6%)	¹⁹⁸Po	(3+)
^198mAt	330(90)# keV			1.0(2) s			(10−)
¹⁹⁹At	85	114	198.99053(5)	6.92(13) s	α (89%)	¹⁹⁵Bi	(9/2−)
¹⁹⁹At	85	114	198.99053(5)	6.92(13) s	β⁺ (11%)	¹⁹⁹Po	(9/2−)
²⁰⁰At	85	115	199.990351(26)	43.2(9) s	α (57%)	¹⁹⁶Bi	(3+)
²⁰⁰At	85	115	199.990351(26)	43.2(9) s	β⁺ (43%)	²⁰⁰Po	(3+)
^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−)
²⁰¹At	85	116	200.988417(9)	85(3) s	β⁺ (29%)	²⁰¹Po	(9/2−)
²⁰²At	85	117	201.98863(3)	184(1) s	β⁺ (88%)	²⁰²Po	(2,3)+
²⁰²At	85	117	201.98863(3)	184(1) s	α (12%)	¹⁹⁸Bi	(2,3)+
^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−
²⁰³At	85	118	202.986942(13)	7.37(13) min	α (31%)	¹⁹⁹Bi	9/2−
²⁰⁴At	85	119	203.987251(26)	9.2(2) min	β⁺ (96%)	²⁰⁴Po	7+
²⁰⁴At	85	119	203.987251(26)	9.2(2) min	α (3.8%)	²⁰⁰Bi	7+
^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−
²⁰⁵At	85	120	204.986074(16)	26.2(5) min	α (10%)	²⁰¹Bi	9/2−
^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)+
²⁰⁶At	85	121	205.986667(22)	30.6(13) min	α (0.9%)	²⁰²Bi	(5)+
^206mAt	807(3) keV			410(80) ns			(10)−
²⁰⁷At	85	122	206.985784(23)	1.80(4) h	β⁺ (91%)	²⁰⁷Po	9/2−
²⁰⁷At	85	122	206.985784(23)	1.80(4) h	α (8.6%)	²⁰³Bi	9/2−
²⁰⁸At	85	123	207.986590(28)	1.63(3) h	β⁺ (99.5%)	²⁰⁸Po	6+
²⁰⁸At	85	123	207.986590(28)	1.63(3) h	α (0.55%)	²⁰⁴Bi	6+
²⁰⁹At	85	124	208.986173(8)	5.41(5) h	β⁺ (96%)	²⁰⁹Po	9/2−
²⁰⁹At	85	124	208.986173(8)	5.41(5) h	α (4.0%)	²⁰⁵Bi	9/2−
²¹⁰At	85	125	209.987148(8)	8.1(4) h	β⁺ (99.8%)	²¹⁰Po	(5)+
²¹⁰At	85	125	209.987148(8)	8.1(4) h	α (0.18%)	²⁰⁶Bi	(5)+
^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−
²¹¹At	85	126	210.9874963(30)	7.214(7) h	α (42%)	²⁰⁷Bi	9/2−
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−)
^212m1At	223(7) keV			0.119(3) s	IT (1%)	²¹²At	(9−)
^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 2]}
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−
²¹⁷At	85	132	217.004719(5)	32.3(4) ms	β⁻ (.012%)	²¹⁷Rn	9/2−
²¹⁸At	85	133	218.008694(12)	1.5(3) s	α (99.9%)	²¹⁴Bi	1−#	Trace^{[n 3]}
²¹⁸At	85	133	218.008694(12)	1.5(3) s	β⁻ (0.10%)	²¹⁸Rn	1−#	Trace^{[n 3]}
²¹⁹At	85	134	219.011162(4)	56(3) s	α (97%)	²¹⁵Bi	5/2−#	Trace^{[n 2]}
²¹⁹At	85	134	219.011162(4)	56(3) s	β⁻ (3.0%)	²¹⁹Rn	5/2−#	Trace^{[n 2]}
²²⁰At	85	135	220.01541(6)	3.71(4) min	β⁻ (92%)	²²⁰Rn	3(−#)
²²⁰At	85	135	220.01541(6)	3.71(4) min	α (8.0%)	²¹⁶Bi	3(−#)
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			3/2−#

^ Abbreviations:
EC: electron capture
IT: isomeric transition
^ ^a ^b Intermediate decay product of ²³⁵U
^ Intermediate decay product of ²³⁸U

Notes

Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic masses from IUPAC, which use expanded uncertainties.

Notes

^ "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.
^ 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 very much less stable toward alpha decay than the lighter isotope.

References

^ 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.
^ ^a ^b ^c ^d ^e ^f Audi, G; Wapstra, A H; Thibault, C; Blachot, J; Bersillon, O (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. Archived from the original (PDF) on 2008-09-23. {{cite journal}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
^ ^a ^b ^c ^d Lavrukhina & Pozdnyakov 1966, p. 232.
^ Rankama, Kalervo (1956). Isotope geology (2nd ed.). Pergamon Press. p. 403. ISBN 978-0-470-70800-2.
^ "Universal Nuclide Chart". nucleonica. {{cite web}}: Unknown parameter |registration= ignored (|url-access= suggested) (help)

Isotope masses from:
- G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. Archived from the original (PDF) on 2008-09-23. {{cite journal}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
Isotopic compositions and standard atomic masses from:
- J. R. de Laeter; J. K. Böhlke; P. De Bièvre; H. Hidaka; H. S. Peiser; K. J. R. Rosman; P. D. P. Taylor (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
- M. E. Wieser (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry. 78 (11): 2051–2066. doi:10.1351/pac200678112051. {{cite journal}}: Unknown parameter |laysummary= ignored (help)
Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.
- G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. Archived from the original (PDF) on 2008-09-23. {{cite journal}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
- National Nuclear Data Center. "NuDat 2.1 database". Brookhaven National Laboratory. Retrieved September 2005. {{cite web}}: Check date values in: |accessdate= (help)
- N. E. Holden (2004). "Table of the Isotopes". In D. R. Lide (ed.). CRC Handbook of Chemistry and Physics (85th ed.). CRC Press. Section 11. ISBN 978-0-8493-0485-9. {{cite book}}: Unknown parameter |nopp= ignored (|no-pp= suggested) (help)

Bibliography

Lavrukhina, A K; Pozdnyakov, A A (1966). Аналитическая химия технеция, прометия, астатина и франция (in Russian). Nauka. {{cite book}}: Invalid |ref=harv (help); Unknown parameter |trans_title= ignored (|trans-title= suggested) (help)

[8] Abbreviations:
EC: electron capture
IT: isomeric transition

[as-9] Intermediate decay product of ²³⁵U

[10] Intermediate decay product of ²³⁸U

[4] "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.

[5] 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 very much less stable toward alpha decay than the lighter isotope.

[NUBASE2020-1] 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.

[ffff-2] ^ ^a ^b ^c ^d ^e ^f Audi, G; Wapstra, A H; Thibault, C; Blachot, J; Bersillon, O (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. Archived from the original (PDF) on 2008-09-23. {{cite journal}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)

[FOOTNOTELavrukhinaPozdnyakov1966232-3] Lavrukhina & Pozdnyakov 1966, p. 232.

[6] Rankama, Kalervo (1956). Isotope geology (2nd ed.). Pergamon Press. p. 403. ISBN 978-0-470-70800-2.

[7] "Universal Nuclide Chart". nucleonica. {{cite web}}: Unknown parameter |registration= ignored (|url-access= suggested) (help)

[1]

[2]

[3]

[a]

[b]

[4]

[5]

[n 1]

[n 2]

[n 3]

Alpha decay

List of isotopes

Notes

See also

Notes

References

Bibliography