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Isotopes of strontium



The alkali earth metal Strontium (Sr) has four stable, naturally occurring isotopes: 84Sr (0.56%), 86Sr (9.86%), 87Sr (7.0%) and 88Sr (82.58%). 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. Thus, there are two sources of 87Sr in any material: that formed during primordial nucleo-synthesis along with 84Sr, 86Sr and 88Sr, as well as that formed by radioactive decay of 87Rb. The ratio 87Sr/86Sr is the parameter typically reported in geologic investigations; ratios in minerals and rocks have values ranging from about 0.7 to greater than 4.0. Because strontium has an atomic radius similar to that of calcium, it readily substitutes for Ca in minerals.

Additional recommended knowledge

Sixteen unstable isotopes are known to exist. Of greatest importance is 90Sr with a half-life of 28.78 years. It is a by-product of nuclear fission which is found in nuclear fallout and presents a health problem since it substitutes for calcium in bone, preventing expulsion from the body. This isotope is one of the best long-lived high-energy beta emitters known, and 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. The 1986 Chernobyl nuclear accident contaminated a vast area with 90Sr.
Standard atomic mass: 87.62(1) u

Table

nuclide
symbol
Z(p) N(n)  
isotopic mass (u)
 
half-life nuclear
spin
representative
isotopic
composition
(mole fraction)
range of natural
variation
(mole fraction)
excitation energy
73Sr 38 35 72.96597(64)# >25 ms 1/2-#
74Sr 38 36 73.95631(54)# 50# ms [>1.5 µs] 0+
75Sr 38 37 74.94995(24) 88(3) ms (3/2-)
76Sr 38 38 75.94177(4) 7.89(7) s 0+
77Sr 38 39 76.937945(10) 9.0(2) s 5/2+
78Sr 38 40 77.932180(8) 159(8) s 0+
79Sr 38 41 78.929708(9) 2.25(10) min 3/2(-)
80Sr 38 42 79.924521(7) 106.3(15) min 0+
81Sr 38 43 80.923212(7) 22.3(4) min 1/2-
82Sr 38 44 81.918402(6) 25.36(3) d 0+
83Sr 38 45 82.917557(11) 32.41(3) h 7/2+
83mSr 259.15(9) keV 4.95(12) s 1/2-
84Sr 38 46 83.913425(3) STABLE 0+ 0.0056(1) 0.0055-0.0058
85Sr 38 47 84.912933(3) 64.853(8) d 9/2+
85mSr 238.66(6) keV 67.63(4) min 1/2-
86Sr 38 48 85.9092602(12) STABLE 0+ 0.0986(1) 0.0975-0.0999
86mSr 2955.68(21) keV 455(7) ns 8+
87Sr 38 49 86.9088771(12) STABLE 9/2+ 0.0700(1) 0.0694-0.0714
87mSr 388.533(3) keV 2.815(12) h 1/2-
88Sr 38 50 87.9056121(12) STABLE 0+ 0.8258(1) 0.8229-0.8275
89Sr 38 51 88.9074507(12) 50.57(3) d 5/2+
90Sr 38 52 89.907738(3) 28.90(3) a 0+
91Sr 38 53 90.910203(5) 9.63(5) h 5/2+
92Sr 38 54 91.911038(4) 2.66(4) h 0+
93Sr 38 55 92.914026(8) 7.423(24) min 5/2+
94Sr 38 56 93.915361(8) 75.3(2) s 0+
95Sr 38 57 94.919359(8) 23.90(14) s 1/2+
96Sr 38 58 95.921697(29) 1.07(1) s 0+
97Sr 38 59 96.926153(21) 429(5) ms 1/2+
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 0+
99Sr 38 61 98.93324(9) 0.269(1) s 3/2+
100Sr 38 62 99.93535(14) 202(3) ms 0+
101Sr 38 63 100.94052(13) 118(3) ms (5/2-)
102Sr 38 64 101.94302(12) 69(6) ms 0+
103Sr 38 65 102.94895(54)# 50# ms [>300 ns]
104Sr 38 66 103.95233(75)# 30# ms [>300 ns] 0+
105Sr 38 67 104.95858(75)# 20# ms [>300 ns]

Notes

  • Evaluated isotopic composition is for most but not all commercial samples.
  • The precision of the isotope abundances and atomic mass is limited through variations. The given ranges should be applicable to any normal terrestrial material.
  • Geologically exceptional samples are known in which the isotopic composition lies outside the reported range. The uncertainty in the atomic mass may exceed the stated value for such specimens.
  • 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

  • Isotope masses from Ame2003 Atomic Mass Evaluation by G. Audi, A.H. Wapstra, C. Thibault, J. Blachot and O. Bersillon in Nuclear Physics A729 (2003).
  • Isotopic compositions and standard atomic masses from Atomic weights of the elements. Review 2000 (IUPAC Technical Report). Pure Appl. Chem. Vol. 75, No. 6, pp. 683-800, (2003) and Atomic Weights Revised (2005).
  • Half-life, spin, and isomer data selected from these sources. Editing notes on this article's talk page.
    • Audi, Bersillon, Blachot, Wapstra. The Nubase2003 evaluation of nuclear and decay properties, Nuc. Phys. A 729, pp. 3-128 (2003).
    • National Nuclear Data Center, Brookhaven National Laboratory. Information extracted from the NuDat 2.1 database (retrieved Sept. 2005).
    • David R. Lide (ed.), Norman E. Holden in CRC Handbook of Chemistry and Physics, 85th Edition, online version. CRC Press. Boca Raton, Florida (2005). Section 11, Table of the Isotopes.


Isotopes of rubidium Isotopes of strontium Isotopes of yttrium
Index to isotope pages
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Isotopes_of_strontium". A list of authors is available in Wikipedia.
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