Isotopes of actinium

Actinides and fission products by half-life v t e
Actinides^[1] by decay chain				Half-life range (a)	Fission products of ²³⁵U by yield^[2]
4n	4n + 1	4n + 2	4n + 3	Half-life range (a)	4.5–7%	0.04–1.25%	<0.001%
²²⁸Ra^№				4–6 a		¹⁵⁵Eu^þ
²⁴⁸Bk^[3]				> 9 a
²⁴⁴Cm^ƒ	²⁴¹Pu^ƒ	²⁵⁰Cf	²²⁷Ac^№	10–29 a	⁹⁰Sr	⁸⁵Kr	^113mCd^þ
²³²U^ƒ		²³⁸Pu^ƒ	²⁴³Cm^ƒ	29–97 a	¹³⁷Cs	¹⁵¹Sm^þ	^121mSn
	²⁴⁹Cf^ƒ	^242mAm^ƒ		141–351 a	No fission products have a half-life in the range of 100 a–210 ka ...
	²⁴¹Am^ƒ		²⁵¹Cf^ƒ^[4]	430–900 a
		²²⁶Ra^№	²⁴⁷Bk	1.3–1.6 ka
²⁴⁰Pu	²²⁹Th	²⁴⁶Cm^ƒ	²⁴³Am^ƒ	4.7–7.4 ka
	²⁴⁵Cm^ƒ	²⁵⁰Cm		8.3–8.5 ka
			²³⁹Pu^ƒ	24.1 ka
		²³⁰Th^№	²³¹Pa^№	32–76 ka
²³⁶Np^ƒ	²³³U^ƒ	²³⁴U^№		150–250 ka	⁹⁹Tc^₡	¹²⁶Sn
²⁴⁸Cm		²⁴²Pu		327–375 ka		⁷⁹Se^₡
				1.33 Ma	¹³⁵Cs^₡
	²³⁷Np^ƒ			1.61–6.5 Ma	⁹³Zr	¹⁰⁷Pd
²³⁶U			²⁴⁷Cm^ƒ	15–24 Ma		¹²⁹I^₡
²⁴⁴Pu				80 Ma	... nor beyond 15.7 Ma^[5]
²³²Th^№		²³⁸U^№	²³⁵U^ƒ№	0.7–14.1 Ga	... nor beyond 15.7 Ma^[5]
₡, has thermal neutron capture cross section in the range of 8–50 barns ƒ, fissile №, primarily a naturally occurring radioactive material (NORM) þ, neutron poison (thermal neutron capture cross section greater than 3k barns)

Actinium (Ac) has no stable isotopes and no characteristic terrestrial isotopic composition, thus a standard atomic mass cannot be given. There are 31 known isotopes, from ²⁰⁶Ac to ²³⁶Ac, and 2 isomers. Two isotopes are found in nature, ²²⁷Ac and ²²⁸Ac, as intermediate decay products of, respectively, ²³⁵U and ²³²Th. ²²⁸Ac is extremely rare, and almost all natural actinium is ²²⁷Ac.

The most stable isotopes are ²²⁷Ac with a half-life of 21.772 years, ²²⁵Ac with a half-life of 10.0 days, and ²²⁶Ac with a half-life of 29.37 hours. All other isotopes have half-lives under 10 hours, and most under a minute. The shortest-lived known isotope is ²¹⁷Ac with a half-life of 69 ns. Actinium also has two meta states.

Purified ²²⁷Ac comes into equilibrium with its decay products (²²⁷Th and ²²³Fr) after 185 days.^[6]

Table

nuclide symbol	historic name	Z(p)	N(n)	isotopic mass (u)	half-life	decay mode(s)^[7]^{[n 1]}	daughter isotope(s)^{[n 2]}	nuclear spin	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)
nuclide symbol	historic name	excitation energy			half-life	decay mode(s)^[7]^{[n 1]}	daughter isotope(s)^{[n 2]}	nuclear spin	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)
²⁰⁵Ac^[8]		89	116		20(+97−9) ms	α	²⁰¹Fr
²⁰⁶Ac		89	117	206.01450(8)	25(7) ms			(3+)
^206m1Ac		80(50) keV			15(6) ms
^206m2Ac		290(110)# keV			41(16) ms			(10−)
²⁰⁷Ac		89	118	207.01195(6)	31(8) ms [27(+11−6) ms]	α	²⁰³Fr	9/2−#
²⁰⁸Ac		89	119	208.01155(6)	97(16) ms [95(+24−16) ms]	α (99%)	²⁰⁴Fr	(3+)
²⁰⁸Ac		89	119	208.01155(6)	97(16) ms [95(+24−16) ms]	β⁺ (1%)	²⁰⁸Ra	(3+)
^208mAc		506(26) keV			28(7) ms [25(+9−5) ms]	α (89%)	²⁰⁴Fr	(10−)
						IT (10%)	²⁰⁸Ac
						β⁺ (1%)	²⁰⁸Ra
²⁰⁹Ac		89	120	209.00949(5)	92(11) ms	α (99%)	²⁰⁵Fr	(9/2−)
²⁰⁹Ac		89	120	209.00949(5)	92(11) ms	β⁺ (1%)	²⁰⁹Ra	(9/2−)
²¹⁰Ac		89	121	210.00944(6)	350(40) ms	α (96%)	²⁰⁶Fr	7+#
²¹⁰Ac		89	121	210.00944(6)	350(40) ms	β⁺ (4%)	²¹⁰Ra	7+#
²¹¹Ac		89	122	211.00773(8)	213(25) ms	α (99.8%)	²⁰⁷Fr	9/2−#
²¹¹Ac		89	122	211.00773(8)	213(25) ms	β⁺ (.2%)	²¹¹Ra	9/2−#
²¹²Ac		89	123	212.00781(7)	920(50) ms	α (97%)	²⁰⁸Fr	6+#
²¹²Ac		89	123	212.00781(7)	920(50) ms	β⁺ (3%)	²¹²Ra	6+#
²¹³Ac		89	124	213.00661(6)	731(17) ms	α	²⁰⁹Fr	(9/2−)#
²¹³Ac		89	124	213.00661(6)	731(17) ms	β⁺ (rare)	²¹³Ra	(9/2−)#
²¹⁴Ac		89	125	214.006902(24)	8.2(2) s	α (89%)	²¹⁰Fr	(5+)#
²¹⁴Ac		89	125	214.006902(24)	8.2(2) s	β⁺ (11%)	²¹⁴Ra	(5+)#
²¹⁵Ac		89	126	215.006454(23)	0.17(1) s	α (99.91%)	²¹¹Fr	9/2−
²¹⁵Ac		89	126	215.006454(23)	0.17(1) s	β⁺ (.09%)	²¹⁵Ra	9/2−
²¹⁶Ac		89	127	216.008720(29)	0.440(16) ms	α	²¹²Fr	(1−)
²¹⁶Ac		89	127	216.008720(29)	0.440(16) ms	β⁺ (7×10⁻⁵%)	²¹⁶Ra	(1−)
^216mAc		44(7) keV			443(7) µs			(9−)
²¹⁷Ac		89	128	217.009347(14)	69(4) ns	α (98%)	²¹³Fr	9/2−
²¹⁷Ac		89	128	217.009347(14)	69(4) ns	β⁺ (2%)	²¹⁷Ra	9/2−
^217mAc		2012(20) keV			740(40) ns			(29/2)+
²¹⁸Ac		89	129	218.01164(5)	1.08(9) µs	α	²¹⁴Fr	(1−)#
^218mAc		584(50)# keV			103(11) ns			(11+)
²¹⁹Ac		89	130	219.01242(5)	11.8(15) µs	α	²¹⁵Fr	9/2−
²¹⁹Ac		89	130	219.01242(5)	11.8(15) µs	β⁺ (10⁻⁶%)	²¹⁹Ra	9/2−
²²⁰Ac		89	131	220.014763(16)	26.36(19) ms	α	²¹⁶Fr	(3−)
²²⁰Ac		89	131	220.014763(16)	26.36(19) ms	β⁺ (5×10⁻⁴%)	²²⁰Ra	(3−)
²²¹Ac		89	132	221.01559(5)	52(2) ms	α	²¹⁷Fr	9/2−#
²²²Ac		89	133	222.017844(6)	5.0(5) s	α (99%)	²¹⁸Fr	1−
²²²Ac		89	133	222.017844(6)	5.0(5) s	β⁺ (1%)	²²²Ra	1−
^222mAc		200(150)# keV			1.05(7) min	α (88.6%)	²¹⁸Fr	high
						IT (10%)	²²²Ac
						β⁺ (1.4%)	²²²Ra
²²³Ac		89	134	223.019137(8)	2.10(5) min	α (99%)	²¹⁹Fr	(5/2−)
						EC (1%)	²²³Ra
						CD (3.2×10⁻⁹%)	²⁰⁹Bi ¹⁴C
²²⁴Ac		89	135	224.021723(4)	2.78(17) h	β⁺ (90.9%)	²²⁴Ra	0−
						α (9.1%)	²²⁰Fr
						β⁻ (1.6%)	²²⁴Th
²²⁵Ac^{[n 3]}		89	136	225.023230(5)	10.0(1) d	α	²²¹Fr	(3/2−)
²²⁵Ac^{[n 3]}		89	136	225.023230(5)	10.0(1) d	CD (6×10⁻¹⁰%)	²¹¹Bi ¹⁴C	(3/2−)
²²⁶Ac		89	137	226.026098(4)	29.37(12) h	β⁻ (83%)	²²⁶Th	(1)(−#)
						EC (17%)	²²⁶Ra
						α (.006%)	²²²Fr
²²⁷Ac	Actinium^{[n 4]}	89	138	227.0277521(26)	21.772(3) y	β⁻ (98.61%)	²²⁷Th	3/2−	Trace^{[n 5]}
²²⁷Ac	Actinium^{[n 4]}	89	138	227.0277521(26)	21.772(3) y	α (1.38%)	²²³Fr	3/2−	Trace^{[n 5]}
²²⁸Ac	Mesothorium 2	89	139	228.0310211(27)	6.13(2) h	β⁻	²²⁸Th	3+	Trace^{[n 6]}
²²⁸Ac	Mesothorium 2	89	139	228.0310211(27)	6.13(2) h	α (5.5×10⁻⁶%)	²²⁴Fr	3+	Trace^{[n 6]}
²²⁹Ac		89	140	229.03302(4)	62.7(5) min	β⁻	²²⁹Th	(3/2+)
²³⁰Ac		89	141	230.03629(32)	122(3) s	β⁻	²³⁰Th	(1+)
²³¹Ac		89	142	231.03856(11)	7.5(1) min	β⁻	²³¹Th	(1/2+)
²³²Ac		89	143	232.04203(11)	119(5) s	β⁻	²³²Th	(1+)
²³³Ac		89	144	233.04455(32)#	145(10) s	β⁻	²³³Th	(1/2+)
²³⁴Ac		89	145	234.04842(43)#	44(7) s	β⁻	²³⁴Th
²³⁵Ac		89	146	235.05123(38)#	40# s	β⁻	²³⁵Th	1/2+#
²³⁶Ac		89	147	236.05530(54)#	2# min	β⁻	²³⁶Th

^ Abbreviations:
CD: Cluster decay
EC: Electron capture
IT: Isomeric transition
^ Bold italics for nearly-stable isotopes (half-life longer than the age of the universe)
^ Has medical uses
^ Source of element's name
^ Intermediate decay product of ²³⁵U
^ Intermediate decay product of ²³²Th

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 mass from IUPAC which use expanded uncertainties.

References

^ Plus radium (element 88). While actually a sub-actinide, it immediately precedes actinium (89) and follows a three-element gap of instability after polonium (84) where no nuclides have half-lives of at least four years (the longest-lived nuclide in the gap is radon-222 with a half life of less than four days). Radium's longest lived isotope, at 1,600 years, thus merits the element's inclusion here.
^ Specifically from thermal neutron fission of uranium-235, e.g. in a typical nuclear reactor.
^ Milsted, J.; Friedman, A. M.; Stevens, C. M. (1965). "The alpha half-life of berkelium-247; a new long-lived isomer of berkelium-248". Nuclear Physics. 71 (2): 299. Bibcode:1965NucPh..71..299M. doi:10.1016/0029-5582(65)90719-4.
"The isotopic analyses disclosed a species of mass 248 in constant abundance in three samples analysed over a period of about 10 months. This was ascribed to an isomer of Bk²⁴⁸ with a half-life greater than 9 [years]. No growth of Cf²⁴⁸ was detected, and a lower limit for the β⁻ half-life can be set at about 10⁴ [years]. No alpha activity attributable to the new isomer has been detected; the alpha half-life is probably greater than 300 [years]."
^ This is the heaviest nuclide with a half-life of at least four years before the "sea of instability".
^ Excluding those "classically stable" nuclides with half-lives significantly in excess of ²³²Th; e.g., while ^113mCd has a half-life of only fourteen years, that of ¹¹³Cd is eight quadrillion years.
^ G. D. Considine, ed. (2005). "Chemical Elements". Van Nostrand's Encyclopedia of Chemistry. Wiley-Interscience. p. 332. ISBN 978-0-471-61525-5.
^ "Universal Nuclide Chart". nucleonica. {{cite web}}: Unknown parameter |registration= ignored (|url-access= suggested) (help)
^ Zhang, Z. Y.; Gan, Z. G.; Ma, L.; Yu, L.; Yang, H. B.; Huang, T. H.; Li, G. S.; Tian, Y. L.; Wang, Y. S.; Xu, X. X.; Huang, M. H.; Luo, C.; Ren, Z. Z.; Zhou, S.G.; Zhou, X. H.; Xu, H. S.; Xiao, G. Q. (January 2014). "α decay of the new neutron-deficient isotope ²⁰⁵Ac". Physical Review C. 89 (1): 014308. doi:10.1103/PhysRevC.89.014308.

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.
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.
- 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)

[8] Abbreviations:
CD: Cluster decay
EC: Electron capture
IT: Isomeric transition

[9] Bold italics for nearly-stable isotopes (half-life longer than the age of the universe)

[11] Has medical uses

[12] Source of element's name

[13] Intermediate decay product of ²³⁵U

[14] Intermediate decay product of ²³²Th

[1] Plus radium (element 88). While actually a sub-actinide, it immediately precedes actinium (89) and follows a three-element gap of instability after polonium (84) where no nuclides have half-lives of at least four years (the longest-lived nuclide in the gap is radon-222 with a half life of less than four days). Radium's longest lived isotope, at 1,600 years, thus merits the element's inclusion here.

[2] Specifically from thermal neutron fission of uranium-235, e.g. in a typical nuclear reactor.

[3] Milsted, J.; Friedman, A. M.; Stevens, C. M. (1965). "The alpha half-life of berkelium-247; a new long-lived isomer of berkelium-248". Nuclear Physics. 71 (2): 299. Bibcode:1965NucPh..71..299M. doi:10.1016/0029-5582(65)90719-4.
"The isotopic analyses disclosed a species of mass 248 in constant abundance in three samples analysed over a period of about 10 months. This was ascribed to an isomer of Bk²⁴⁸ with a half-life greater than 9 [years]. No growth of Cf²⁴⁸ was detected, and a lower limit for the β⁻ half-life can be set at about 10⁴ [years]. No alpha activity attributable to the new isomer has been detected; the alpha half-life is probably greater than 300 [years]."

[4] This is the heaviest nuclide with a half-life of at least four years before the "sea of instability".

[5] Excluding those "classically stable" nuclides with half-lives significantly in excess of ²³²Th; e.g., while ^113mCd has a half-life of only fourteen years, that of ¹¹³Cd is eight quadrillion years.

[nostrand332-6] G. D. Considine, ed. (2005). "Chemical Elements". Van Nostrand's Encyclopedia of Chemistry. Wiley-Interscience. p. 332. ISBN 978-0-471-61525-5.

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

[ZhangEtAl2014-10] Zhang, Z. Y.; Gan, Z. G.; Ma, L.; Yu, L.; Yang, H. B.; Huang, T. H.; Li, G. S.; Tian, Y. L.; Wang, Y. S.; Xu, X. X.; Huang, M. H.; Luo, C.; Ren, Z. Z.; Zhou, S.G.; Zhou, X. H.; Xu, H. S.; Xiao, G. Q. (January 2014). "α decay of the new neutron-deficient isotope ²⁰⁵Ac". Physical Review C. 89 (1): 014308. doi:10.1103/PhysRevC.89.014308.

[1]

[2]

[3]

[4]

[5]

[6]

[7]

[n 1]

[n 2]

[8]

[n 3]

[n 4]

[n 5]

[n 6]

Table

Notes

See also

References