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
- ^ Phys. Rev. C 73 044326 (April 2006)
- ^ 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.
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