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Isotopes of Thorium

List, data and properties of all known isotopes of Thorium.

Content
Atomic properties
Decay properties
NMR active nuclides
Radiation protection
References
Thorium isotopes

All atomic nuclei of the chemical element thorium are summarized under thorium isotopes; these all consist of an atomic nucleus with 90 protons and, in the uncharged state, 90 electrons. The difference between the individual thorium isotopes is based on the number of neutrons in the nucleus.

Terrestrial thorium deposits consist of practically 99.98% of the nuclide 232Th and 0 .02% from 230Th; in addition, the 4 isotopes 227Th, 228Th, 231Th and 234Th and 234 are found in small traces and as intermediate products of radioactive decay processes. sup>Th.

Thorium isotopes are used in various fields. In the nuclear energy industry, for example, they are used as fuel in so-called thorium fuel cells. In medical diagnostics, thorium isotopes can be used to produce imaging agents. They can also be used in the manufacture of ceramics and glasses as they increase the hardness and durability of these materials.

However, it is important to note that all thorium isotopes are radioactive and therefore appropriate precautions must be taken in use and handling to protect the health and safety of people and the environment.

The relative atomic mass is given as 232.0377(4) u.

Newly discovered or observed thorium isotopes: Th-207 (2022).

 

Isotope Table: Thorium

The two following tables list the most important data and properties of the Thorium isotopes. Further information on the individual Thorium isotopes is listed on separate pages and can be accessed via the link in column 1.

 

Atomic Properties

Isotope
Nuclide		ENAtomic Mass
[Nuclear Mass]
{Mass Excess}		Spin I
(h/2π)		Parent
123456
Thorium-20720790Th117207 u
[206.9506342 u]
{0 MeV}
Thorium-20820890Th118208.01791(4) u
[207.9685442 u]
{16.68306 MeV}		0+
Thorium-20920990Th119209.01757(15) u
[208.9682042 u]
{16.36635 MeV}		(13/2+)
Thorium-21021090Th120210.015093(20) u
[209.9657272 u]
{14.05904 MeV}		0+
Thorium-21121190Th121211.01493(8) u
[210.9655642 u]
{13.90721 MeV}
Thorium-21221290Th122212.013001(11) u
[211.9636352 u]
{12.11035 MeV}		0+
Thorium-21321390Th123213.013011(10) u
[212.9636452 u]
{12.11967 MeV}		(5/2-)217U
Thorium-21421490Th124214.011481(11) u
[213.9621152 u]
{10.69448 MeV}		0+218U
Thorium-214m214m90Th124214.011481(11) u
[213.9621152 u]
{10.69448 MeV}		(8+)
Thorium-21521590Th125215.011725(9) u
[214.9623592 u]
{10.92177 MeV}		(1/2-)219U
Thorium-215m215m90Th125215.011725(9) u
[214.9623592 u]
{10.92177 MeV}
Thorium-21621690Th126216.011056(13) u
[215.9616902 u]
{10.2986 MeV}		0+
Thorium-216m1216m190Th126216.011056(13) u
[215.9616902 u]
{10.2986 MeV}		8+
Thorium-216m2216m290Th126216.011056(13) u
[215.9616902 u]
{10.2986 MeV}		11-
Thorium-216m3216m390Th126216.011056(13) u
[215.9616902 u]
{10.2986 MeV}		(14+)
Thorium-21721790Th127217.013103(11) u
[216.9637372 u]
{12.20537 MeV}		(9/2+)221U
Thorium-217m1217m190Th127217.013103(11) u
[216.9637372 u]
{12.20537 MeV}		(15/2-)
Thorium-21821890Th128218.013276(11) u
[217.9639102 u]
{12.36651 MeV}		0+222U
Thorium-21921990Th129219.01554(5) u
[218.9661742 u]
{14.47542 MeV}		(9/2+)223U
Thorium-22022090Th130220.015748(24) u
[219.9663822 u]
{14.66917 MeV}		0+224U
Thorium-22122190Th131221.018186(9) u
[220.9688202 u]
{16.94015 MeV}		(7/2+)225U
Thorium-22222290Th132222.018468(13) u
[221.9691022 u]
{17.20283 MeV}		0+226U
Thorium-22322390Th133223.020811(9) u
[222.9714452 u]
{19.38532 MeV}		(5/2)+227U
Thorium-22422490Th134224.021464(11) u
[223.9720982 u]
{19.99359 MeV}		0+228U
Thorium-22522590Th135225.023951(5) u
[224.9745852 u]
{22.31021 MeV}		(3/2+)229U
Thorium-22622690Th136226.024904(5) u
[225.9755382 u]
{23.19793 MeV}		0+230U
226Ac
226Pa
Thorium-22722790Th137227.0277025(22) u
[226.9783367 u]
{25.80471 MeV}		(1/2+)231U
227Ac
227Pa
Thorium-22822890Th138228.0287398(19) u
[227.979374 u]
{26.77095 MeV}		0+232U
228Ac
228Pa
Thorium-22922990Th139229.0317614(26) u
[228.9823956 u]
{29.58555 MeV}		5/2+233U
229Ac
Thorium-229m229m90Th139229.0317614(26) u
[228.9823956 u]
{29.58555 MeV}		3/2+
Thorium-23023090Th140230.0331323(2) u
[229.9837665 u]
{30.86254 MeV}		0+234U
230Ac
230Pa
Thorium-23123190Th141231.0363028(13) u
[230.986937 u]
{33.81584 MeV}		5/2+235U
231Ac
Thorium-23223290Th142232.03806(2) u
[231.9886942 u]
{35.45266 MeV}		0+236U
232Ac
232Pa
Thorium-23323390Th143233.0415802(15) u
[232.9922144 u]
{38.73171 MeV}		1/2+233Ac
Thorium-23423490Th144234.0435999(28) u
[233.9942341 u]
{40.61305 MeV}		0+238U
234Ac
Thorium-23523590Th145235.047255(14) u
[234.9978892 u]
{44.01775 MeV}		(1/2+)
Thorium-23623690Th146236.049657(15) u
[236.0002912 u]
{46.2552 MeV}		0+
Thorium-23723790Th147237.053629(17) u
[237.0042632 u]
{49.95509 MeV}		(5/2+)
Thorium-23823890Th148238.05639(30) u
[238.0070242 u]
{52.52695 MeV}		0+

 

Radioactive Decay Properties

IsotopeRadioactive DecayExtern
Half-lifeDecay ModeProbabilityEnergy
789101112
Th-2070.0097 sα → 203Ra8.167(21) MeVAL
Th-2081.7 msα → 204Ra100 %8.20(3) MeVAL
Th-2092.5 msα → 205Ra8.10(14) MeVAL
Th-2101.6(4) msα → 206Ra
EC/β+ → 210Ac		99 %
ca. 1 %		8.069(6) MeV
5.27(6) MeV		AL
Th-21137 msα → 207Ra
&epsilon → 211Ac		?
?		7.94(5) MeV
6.71(9) MeV		AL
Th-21231.7(13) msα → 208Ra
EC/β+ → 212Ac		ca. 99.7 %
ca. 0.3 %		7.958(5) MeV
4.83(5) MeV		AL
Th-213144(21) msα → 209Ra≤ 100 %7.837(7) MeVAL
Th-21487(10) msα → 210Ra100 %7.827(5) MeVAL
Th-214m1.24(12) μsIso → 214Th100 %
Th-2151.2(2) sα → 211Ra100 %7.665(4) MeVAL
Th-215m0.77(6) μsIso → 215Th100 %
Th-21626.0(2) msα → 212Ra≤ 100 %8.072(4) MeVAL
Th-216m1134(4) μsα → 212Ra2.8(9) %
Th-216m20.58(3) μs
Th-216m30.74(7) μs
Th-2170.252(4) msα → 213Ra100 %9.435(4) MeVAL
Th-217m10.141(50) msIso → 217Th100 %AL
Th-218117(9) nsα → 214Ra100 %9.849(9) MeVAL
Th-2191.05(3) μsα → 215Ra100 %9.51(5) MeVAL
Th-2209.7(6) μsα → 216Ra
EC → 220Ac		≤ 100 %
<< 1 %		8.953(20) MeV
0.925(23) MeV		AL
Th-2211.74(3) msα → 217Ra100 %8.625(4) MeVAL
Th-2222.24(3) msα → 218Ra100 %8.127(5) MeVAL
Th-2230.60(2) sα → 219Ra100 %7.567(4) MeVAL
Th-2241.04(2) sα → 220Ra100 %7.299(6) MeVAL
Th-2258.75(4) minα → 221Ra
EC → 225Ac		ca. 90 %
ca. 10 %		6.9214(21) MeV
0.637(7) MeV		AL
Th-22630.57(10) minα → 222Ra100 %6.4525(10) MeVAL
Th-22718.697(7) dα → 223Ra100 %6.1466(1) MeVAL
Th-2281.9116(16) aα → 224Ra100 %5.52015(22) MeVAL
Th-2297880(120) aα → 225Ra100 %5.1676(10) MeVAL
Th-229m7(1) μsIso → 229Th
Th-2307.54(3) × 104 aα → 226Ra
SF div
CD → 24Ne		ca. 100 %
<< 1 %
<< 1 %		4.7700(15) MeV

AL
Th-23125.57(8) hβ- → 231Pa100 %3.915(15) MeVAL
Th-2321.40(1) × 1010 aα → 228Ra
SF div		> 99 %
<< 1 %		4.0816(14) MeV
AL
Th-23321.83(4) minβ- → 233Pa100 %1.2422(11) MeVAL
Th-23424.10(3) dβ- → 234Pa100 %0.274(3) MeVAL
Th-2357.2(1) minβ- → 235Pa100 %1.729(19) MeVAL
Th-23637.5(2) minβ- → 236Pa100 %0.921(20) MeVAL
Th-2374.8(5) minβ- → 237Pa100 %2.427(21) MeVAL
Th-2389.4(20) minβ- → 238Pa100 %1.63(28) MeVAL

 

Notes (related to the columns):

1 - name of the nuclide, isotope.
2 - E: isotope symbol with mass number (superscript; number of nucleons) and Atomic number (subscript; number of protons).
3 - N: number of neutrons.
4 - relative atomic mass of the Thorium isotope (isotopic mass including electrons) and the mass of the atomic nucleus in square brackets (nuclear mass, nuclide mass without electrons), each related to 12C = 12.00000 [2]. In addition, the mass excess is given in MeV.
5 - nuclear spin I, unit: h/2π.
6 - source nuclides: Possible, assumed or actual source nuclides (mother nuclides, parent nuclides). If applicable, the corresponding decay modes can be found in the data for the respective starting nuclide.

7 - isotope notation in short form.
8 - decay: half-live of the Thorium isotope (a = years; ; d = days; h = hours; min = minutes; s = seconds).
9 - decay mode: type of decay into the respective daughter nuclides with n = neutron emission; p = proton emission; α = alpha decay; β- = beta minus decay with electron emission; EC = electron capture; β+ = positron emission; ε = β+ and/or EC; Iso = isomeric transition; CD = cluster decay; SF = spontaneous decay.
10 - decay probability in percent (%).
11 - decay energy; Particle energy related to decay type.
12 - other information and notes: AL = Adopted Levels (link to external data [1]).

Miscellaneous:

()- Numbers in brackets: uncertainty to represent the spread of the reported value.
~ - Theoretical values or systematic trends.
  - unlisted-: Nuclides that have already been mentioned in the literature but for some reason can no longer be found in the current nuclide tables because their discovery e.g. has not confirmed.

 

NMR active Thorium nuclides

Nuclide
quantity 1)
spin		Nuclear
magnetic
moment
μ/μN		Gyromagnetic ratio
{Quadrupole moment}		Resonant
frequency
v0 bei 1 T		Relative
sensitivity
H0 = const.
v0 = const. 3)
229Th

5/2+		+ 0,46(4)0,40
{3,110(6)}		1,400,00042
0,3843

1) Quantity Percentage of natural occurrence.

2) Gyromagnetic ratio: 107 rad T-1 s-1
    Quadrupole moment: Q [barn] = [100 fm2]

3) Related to 1H = 1,000.

 

Radiation Protection

According to the Radiation Protection Ordinance (StrlSchV 2018, Germany), the following values (columns 1 to 7) apply to the handling of Thorium radionuclides:

NuclideLimit ValueHASS limitSCDaughter NuclidesHalf-life
Th-226+107 Bq1000 Bq/g10 Bq cm-2Ra-222, Rn-218, Po-21430.6 min
Th-227104 Bq10 Bq/g0,1 Bq cm-218.7 d
Th-228+104 Bq0,1 Bq/g0,04 TBq0,1 Bq cm-2Ra-224, Rn-220, Po-216,
Pb-212, Bi-212, Tl-208,
Po-212		1.9 a
Th-229+103 Bq0,1 Bq/g0,01 TBq0,1 Bq cm-2Ra-225, Ac-225, Fr-221,
At-217, Bi-213, Tl-209,
Po-213, Pb-209		7300 a
Th-230104 Bq0,1 Bq/g0,1 Bq cm-275000 a
Th-231107 Bq1000 Bq/g10 TBq100 Bq cm-225.5 h
Th-232104 Bq10 Bq/g0,1 Bq cm-21.4 × 1010 a
Th234+105 Bq100 Bq/g2 TBq100 Bq cm-2Pa-234m, Pa-23424.1 d

(HASS = High-Activity Sealed Radioactive Sources; SC = surface contamination)

 

Literature Sources and References

Properties of the Thorium nucleides

[1] - NuDat: National Nuclear Data Center, Brookhaven National Laboratory, based on ENSDF and the Nuclear Wallet Cards.

[2] - G. Audi et. al.: The NUBASE evaluation of nuclear and decay properties. Nuclear Physics, (2003), DOI 10.1016/j.nuclphysa.2003.11.001.

[3] - Live Chart of Nuclides. Nuclear structure and decay data.

Thorium: NMR properties - 229Th-NMR

[4] - N. J. Stone: Table of nuclear magnetic dipole and electric quadrupole moments. Atomic Data and Nuclear Data Tables, (2005), DOI 10.1016/j.adt.2005.04.001.

[5] - Pekka Pyykkö: Year-2008 nuclear quadrupole moments. Molecular Physics, (2008), DOI 10.1080/00268970802018367.

[6] - Pekka Pyykkö: Year-2017 nuclear quadrupole moments. Molecular Physics, (2018), DOI 10.1080/00268976.2018.1426131.

[7] - N. J. Stone: Table of recommended nuclear magnetic dipole moments. IAEA, (2019).

More sources:

[8] - Isotopic abundances, atomic weights and isotopic masses: see respective keyword.

[9] - C. Fry, M. Thoennessen:
Discovery of actinium, thorium, protactinium, and uranium isotopes.
In: Atomic Data and Nuclear Data Tables, (2013), DOI 10.1016/j.adt.2012.03.002.

 

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