Isotopes of strontium

The alkaline earth metal strontium (₃₈Sr) has four stable, naturally occurring isotopes: ⁸⁴Sr (0.56%), ⁸⁶Sr (9.86%), ⁸⁷Sr (7.0%) and ⁸⁸Sr (82.58%). Its standard atomic weight is 87.62(1).

Isotopes of strontium (₃₈Sr)

Main isotopes[1] Decay abun­dance half-life (t1/2) mode pro­duct 82Sr synth 25.36 d ε 82Rb 83Sr synth 1.35 d ε 83Rb β+ 83Rb γ – 84Sr 0.56% stable 85Sr synth 64.84 d ε 85Rb γ – 86Sr 9.86% stable 87Sr 7% stable 88Sr 82.6% stable 89Sr synth 50.52 d β− 89Y 90Sr trace 28.90 y β− 90Y
Standard atomic weight Ar°(Sr)
	87.62±0.01[2] 87.62±0.01 (abridged)[3]
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Only ⁸⁷Sr is radiogenic; it is produced by decay from the radioactive alkali metal ⁸⁷Rb, which has a half-life of 4.88 × 10¹⁰ years (i.e. more than three times longer than the current age of the universe). Thus, there are two sources of ⁸⁷Sr in any material: primordial, formed during nucleosynthesis along with ⁸⁴Sr, ⁸⁶Sr and ⁸⁸Sr; and that formed by radioactive decay of ⁸⁷Rb. The ratio ⁸⁷Sr/⁸⁶Sr is the parameter typically reported in geologic investigations;^[4] ratios in minerals and rocks have values ranging from about 0.7 to greater than 4.0 (see rubidium–strontium dating). Because strontium has an electron configuration similar to that of calcium, it readily substitutes for calcium in minerals.

In addition to the four stable isotopes, thirty-two unstable isotopes of strontium are known to exist, ranging from ⁷³Sr to ¹⁰⁸Sr. Radioactive isotopes of strontium primarily decay into the neighbouring elements yttrium (⁸⁹Sr and heavier isotopes, via beta minus decay) and rubidium (⁸⁵Sr, ⁸³Sr and lighter isotopes, via positron emission or electron capture). The longest-lived of these isotopes, and the most relevantly studied, are ⁹⁰Sr with a half-life of 28.9 years, ⁸⁵Sr with a half-life of 64.853 days, and ⁸⁹Sr (⁸⁹Sr) with a half-life of 50.57 days. All other strontium isotopes have half-lives shorter than 50 days, most under 100 minutes.

Strontium-89 is an artificial radioisotope used in treatment of bone cancer;^[5] this application utilizes its chemical similarity to calcium, which allows it to substitute calcium in bone structures. In circumstances where cancer patients have widespread and painful bony metastases, the administration of ⁸⁹Sr results in the delivery of beta particles directly to the cancerous portions of the bone, where calcium turnover is greatest. Strontium-90 is a by-product of nuclear fission, present in nuclear fallout. The 1986 Chernobyl nuclear accident contaminated a vast area with ⁹⁰Sr.^[6] It causes health problems, as it substitutes for calcium in bone, preventing expulsion from the body. Because it is a long-lived high-energy beta emitter, it is used in SNAP (Systems for Nuclear Auxiliary Power) devices. These devices hold promise for use in spacecraft, remote weather stations, navigational buoys, etc., where a lightweight, long-lived, nuclear-electric power source is required.

In 2020, researchers have found that mirror nuclides ⁷³Sr and ⁷³Br were found to not behave identically to each other as expected.^[7]

List of isotopes

Nuclide [n 1]	Z	N	Isotopic mass (Da) [n 2][n 3]	Half-life [n 4]	Decay mode [n 5]	Daughter isotope [n 6][n 7]	Spin and parity [n 8][n 4]	Natural abundance (mole fraction)
	Excitation energy							Normal proportion	Range of variation
73Sr	38	35	72.96597(64)#	>25 ms	β+ (>99.9%)	73Rb	1/2−#
					β+, p (<.1%)	72Kr
74Sr	38	36	73.95631(54)#	50# ms [>1.5 μs]	β+	74Rb	0+
75Sr	38	37	74.94995(24)	88(3) ms	β+ (93.5%)	75Rb	(3/2−)
					β+, p (6.5%)	74Kr
76Sr	38	38	75.94177(4)	7.89(7) s	β+	76Rb	0+
77Sr	38	39	76.937945(10)	9.0(2) s	β+ (99.75%)	77Rb	5/2+
					β+, p (.25%)	76Kr
78Sr	38	40	77.932180(8)	159(8) s	β+	78Rb	0+
79Sr	38	41	78.929708(9)	2.25(10) min	β+	79Rb	3/2(−)
80Sr	38	42	79.924521(7)	106.3(15) min	β+	80Rb	0+
81Sr	38	43	80.923212(7)	22.3(4) min	β+	81Rb	1/2−
82Sr	38	44	81.918402(6)	25.36(3) d	EC	82Rb	0+
83Sr	38	45	82.917557(11)	32.41(3) h	β+	83Rb	7/2+
83mSr	259.15(9) keV			4.95(12) s	IT	83Sr	1/2−
84Sr	38	46	83.913425(3)	Observationally Stable[n 9]			0+	0.0056	0.0055–0.0058
85Sr	38	47	84.912933(3)	64.853(8) d	EC	85Rb	9/2+
85mSr	238.66(6) keV			67.63(4) min	IT (86.6%)	85Sr	1/2−
					β+ (13.4%)	85Rb
86Sr	38	48	85.9092607309(91)	Stable			0+	0.0986	0.0975–0.0999
86mSr	2955.68(21) keV			455(7) ns			8+
87Sr[n 10]	38	49	86.9088774970(91)	Stable			9/2+	0.0700	0.0694–0.0714
87mSr	388.533(3) keV			2.815(12) h	IT (99.7%)	87Sr	1/2−
					EC (.3%)	87Rb
88Sr[n 11]	38	50	87.9056122571(97)	Stable			0+	0.8258	0.8229–0.8275
89Sr[n 11]	38	51	88.9074507(12)	50.57(3) d	β−	89Y	5/2+
90Sr[n 11]	38	52	89.907738(3)	28.90(3) y	β−	90Y	0+
91Sr	38	53	90.910203(5)	9.63(5) h	β−	91Y	5/2+
92Sr	38	54	91.911038(4)	2.66(4) h	β−	92Y	0+
93Sr	38	55	92.914026(8)	7.423(24) min	β−	93Y	5/2+
94Sr	38	56	93.915361(8)	75.3(2) s	β−	94Y	0+
95Sr	38	57	94.919359(8)	23.90(14) s	β−	95Y	1/2+
96Sr	38	58	95.921697(29)	1.07(1) s	β−	96Y	0+
97Sr	38	59	96.926153(21)	429(5) ms	β− (99.95%)	97Y	1/2+
					β−, n (.05%)	96Y
97m1Sr	308.13(11) keV			170(10) ns			(7/2)+
97m2Sr	830.8(2) keV			255(10) ns			(11/2−)#
98Sr	38	60	97.928453(28)	0.653(2) s	β− (99.75%)	98Y	0+
					β−, n (.25%)	97Y
99Sr	38	61	98.93324(9)	0.269(1) s	β− (99.9%)	99Y	3/2+
					β−, n (.1%)	98Y
100Sr	38	62	99.93535(14)	202(3) ms	β− (99.02%)	100Y	0+
					β−, n (.98%)	99Y
101Sr	38	63	100.94052(13)	118(3) ms	β− (97.63%)	101Y	(5/2−)
					β−, n (2.37%)	100Y
102Sr	38	64	101.94302(12)	69(6) ms	β− (94.5%)	102Y	0+
					β−, n (5.5%)	101Y
103Sr	38	65	102.94895(54)#	50# ms [>300 ns]	β−	103Y
104Sr	38	66	103.95233(75)#	30# ms [>300 ns]	β−	104Y	0+
105Sr	38	67	104.95858(75)#	20# ms [>300 ns]
106Sr[8]	38	68
107Sr[8]	38	69
108Sr[9]	38	70
This table header & footer: view

1. ^mSr – 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. # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
5. Modes of decay:

   EC:	Electron capture
   IT:	Isomeric transition
   n:	Neutron emission
   p:	Proton emission

6. Bold italics symbol as daughter – Daughter product is nearly stable.
7. Bold symbol as daughter – Daughter product is stable.
8. ( ) spin value – Indicates spin with weak assignment arguments.
9. Believed to decay by β⁺β⁺ to ⁸⁴Kr
10. Used in rubidium–strontium dating
11. Fission product

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. "Standard Atomic Weights: Strontium". CIAAW. 1969.
3. Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
4. Dickin, Alan P. (2018). Radiogenic Isotope Geology (3 ed.). Cambridge: Cambridge University Press. ISBN 978-1-107-09944-9.
5. Reddy, Eashwer K.; Robinson, Ralph G.; Mansfield, Carl M. (January 1986). "Strontium 89 for Palliation of Bone Metastases". Journal of the National Medical Association. 78 (1): 27–32. ISSN 0027-9684. PMC 2571189. PMID 2419578.
6. Wilken, R.D.; Diehl, R. (1987). "Strontium-90 in environmental samples from Northern Germany before and after the Chernobyl accident". Radiochimica Acta. 41 (4): 157–162. doi:10.1524/ract.1987.41.4.157. S2CID 99369165.
7. "Discovery by UMass Lowell-led team challenges nuclear theory". Space Daily. Retrieved 2022-06-26.
8. Ohnishi, Tetsuya; Kubo, Toshiyuki; Kusaka, Kensuke; et al. (2010). "Identification of 45 New Neutron-Rich Isotopes Produced by In-Flight Fission of a ²³⁸U Beam at 345 MeV/nucleon". J. Phys. Soc. Jpn. 79 (7). Physical Society of Japan: 073201. arXiv:1006.0305. Bibcode:2010JPSJ...79g3201T. doi:10.1143/JPSJ.79.073201.
9. Sumikama, T.; et al. (2021). "Observation of new neutron-rich isotopes in the vicinity of ¹¹⁰Zr". Physical Review C. 103 (1): 014614. Bibcode:2021PhRvC.103a4614S. doi:10.1103/PhysRevC.103.014614. hdl:10261/260248. S2CID 234019083.

• 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
• Isotopic compositions and standard atomic masses from:
  • de Laeter, John Robert; Böhlke, John Karl; De Bièvre, Paul; Hidaka, Hiroshi; Peiser, H. Steffen; Rosman, Kevin J. R.; Taylor, Philip D. P. (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
  • Wieser, Michael E. (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry. 78 (11): 2051–2066. doi:10.1351/pac200678112051.
• "News & Notices: Standard Atomic Weights Revised". International Union of Pure and Applied Chemistry. 19 October 2005.
• 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 2.x 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.