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Isotopes of thorium



Although thorium (Th) has multiple isotopes, none of these isotopes are stable; however, one isotope is relatively stable (232Th). As such, it is considered a monoisotopic element. It has a characteristic terrestrial isotopic composition and thus an atomic mass can be given.
Standard atomic mass: 232.03806(2) u

Additional recommended knowledge

Isotopes of thorium occurring within the radioactive disintegration chains of actinium, thorium and uranium were known as:

  • radio-actinium : 227Th
  • radio-thorium : 228Th
  • ionium : 230Th
  • uranium Y : 231Th
  • uranium X1 : 234Th

Twenty-seven radioisotopes have been characterized, with the most abundant and/or stable being 232Th with a half-life of 14.05 billion years, 230Th with a half-life of 75,380 years, 229Th with a half-life of 7340 years, and 228Th with a half-life of 1.92 years. All of the remaining radioactive isotopes have half-lives that are less than thirty days and the majority of these have half-lives that are less than ten minutes. One isotope, 229Th, has a nuclear isomer (or metastable state) with a remarkably low excitation energy of 3.5 eV. [1]

The known isotopes of thorium range in atomic weight from 210 u (210Th)[2] to 236 u (236Th).

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
209Th 90 119 209.01772(11) 7(5) ms [3.8(+69-15)] 5/2-#
210Th 90 120 210.015075(27) 17(11) ms [9(+17-4) ms] 0+
211Th 90 121 211.01493(8) 48(20) ms [0.04(+3-1) s] 5/2-#
212Th 90 122 212.01298(2) 36(15) ms [30(+20-10) ms] 0+
213Th 90 123 213.01301(8) 140(25) ms 5/2-#
214Th 90 124 214.011500(18) 100(25) ms 0+
215Th 90 125 215.011730(29) 1.2(2) s (1/2-)
216Th 90 126 216.011062(14) 26.8(3) ms 0+
216m1Th 2042(13) keV 137(4) µs (8+)
216m2Th 2637(20) keV 615(55) ns (11-)
217Th 90 127 217.013114(22) 240(5) µs (9/2+)
218Th 90 128 218.013284(14) 109(13) ns 0+
219Th 90 129 219.01554(5) 1.05(3) µs 9/2+#
220Th 90 130 220.015748(24) 9.7(6) µs 0+
221Th 90 131 221.018184(10) 1.73(3) ms (7/2+)
222Th 90 132 222.018468(13) 2.237(13) ms 0+
223Th 90 133 223.020811(10) 0.60(2) s (5/2)+
224Th 90 134 224.021467(12) 1.05(2) s 0+
225Th 90 135 225.023951(5) 8.72(4) min (3/2)+
226Th 90 136 226.024903(5) 30.57(10) min 0+
227Th 90 137 227.0277041(27) 18.68(9) d 1/2+
228Th 90 138 228.0287411(24) 1.9116(16) a 0+
229Th 90 139 229.031762(3) 7.34(16)E+3 a 5/2+
229mTh 0.0035(10) keV 70(50) h 3/2+
230Th 90 140 230.0331338(19) 7.538(30)E+4 a 0+
231Th 90 141 231.0363043(19) 25.52(1) h 5/2+
232Th 90 142 232.0380553(21) 1.405(6)E+10 a 0+ 1.0000
233Th 90 143 233.0415818(21) 21.83(4) min 1/2+
234Th 90 144 234.043601(4) 24.10(3) d 0+
235Th 90 145 235.04751(5) 7.2(1) min (1/2+)#
236Th 90 146 236.04987(21)# 37.5(2) min 0+
237Th 90 147 237.05389(39)# 4.8(5) min 5/2+#
238Th 90 148 238.0565(3)# 9.4(20) min 0+

Notes

  • 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

  1. ^ Phys. Rev. C 73 044326 (April 2006)
  2. ^ Phys. Rev. C 52, 113–116 (1995)
  • 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 actinium Isotopes of thorium Isotopes of protactinium
Index to isotope pages
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Isotopes_of_thorium". A list of authors is available in Wikipedia.
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