Isotopes of thorium
List of isotopes
Bold for nuclides with half-lives longer than the age of the universe (nearly stable) Abbreviations: CD: Cluster decay EC: Electron capture IT: Isomeric transition SF: Spontaneous fission Bold for stable isotopes Intermediate decay product of ²³⁵U Intermediate decay product of ²³²Th Used in Uranium–thorium dating Intermediate decay product of ²³⁸U Primordial radionuclide

Isotopes of thorium

Section Title: List of isotopes
Table Section Text: Bold for nuclides with half-lives longer than the age of the universe (nearly stable) Abbreviations: CD: Cluster decay EC: Electron capture IT: Isomeric transition SF: Spontaneous fission Bold for stable isotopes Intermediate decay product of ²³⁵U Intermediate decay product of ²³²Th Used in Uranium–thorium dating Intermediate decay product of ²³⁸U Primordial radionuclide

nuclide symbol	historic name	Z(p)	N(n)	isotopic mass (u)	half-life	decay mode(s)	daughter isotope(s)	nuclear spin and parity	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)

excitation energy

208Th	90	118	1.7(+1.7-0.6) ms	α	204Ra	0+

209Th	90	119	209.01772(11)	7(5) ms [3.8(+69−15)]	α	205Ra	5/2−#

210Th	90	120	210.015075(27)	17(11) ms [9(+17−4) ms]	α	206Ra	0+

β+ (rare)	210Ac

211Th	90	121	211.01493(8)	48(20) ms [0.04(+3−1) s]	α	207Ra	5/2−#

β+ (rare)	211Ac

212Th	90	122	212.01298(2)	36(15) ms [30(+20-10) ms]	α (99.7%)	208Ra	0+

β+ (.3%)	212Ac

213Th	90	123	213.01301(8)	140(25) ms	α	209Ra	5/2−#

β+ (rare)	213Ac

214Th	90	124	214.011500(18)	100(25) ms	α	210Ra	0+

215Th	90	125	215.011730(29)	1.2(2) s	α	211Ra	(1/2−)

216Th	90	126	216.011062(14)	26.8(3) ms	α (99.99%)	212Ra	0+

β+ (.006%)	216Ac

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	α	213Ra	(9/2+)

218Th	90	128	218.013284(14)	109(13) ns	α	214Ra	0+

219Th	90	129	219.01554(5)	1.05(3) µs	α	215Ra	9/2+#

β+ (10−7%)	219Ac

220Th	90	130	220.015748(24)	9.7(6) µs	α	216Ra	0+

EC (2×10−7%)	220Ac

221Th	90	131	221.018184(10)	1.73(3) ms	α	217Ra	(7/2+)

222Th	90	132	222.018468(13)	2.237(13) ms	α	218Ra	0+

EC (1.3×10−8%)	222Ac

223Th	90	133	223.020811(10)	0.60(2) s	α	219Ra	(5/2)+

224Th	90	134	224.021467(12)	1.05(2) s	α	220Ra	0+

β+β+ (rare)	224Ra

225Th	90	135	225.023951(5)	8.72(4) min	α (90%)	221Ra	(3/2)+

EC (10%)	225Ac

226Th	90	136	226.024903(5)	30.57(10) min	α	222Ra	0+

227Th	Radioactinium	90	137	227.0277041(27)	18.68(9) d	α	223Ra	1/2+	Trace

228Th	Radiothorium	90	138	228.0287411(24)	1.9116(16) y	α	224Ra	0+	Trace

CD (1.3×10−11%)	208Pb 20O

229Th	90	139	229.031762(3)	7.34(16)×103 y	α	225Ra	5/2+

229mTh	7.6(5) eV	70(50) h	IT	229Th	3/2+

230Th	Ionium	90	140	230.0331338(19)	7.538(30)×104 y	α	226Ra	0+	0.0002(2)

CD (5.6×10−11%)	206Hg 24Ne

SF (5×10−11%)	(Various)

231Th	Uranium Y	90	141	231.0363043(19)	25.52(1) h	β−	231Pa	5/2+	Trace

α (10−8%)	227Ra

232Th	Thorium	90	142	232.0380553(21)	1.405(6)×1010 y	α	228Ra	0+	0.9998(2)

β−β− (rare)	232U

SF (1.1×10−9%)	(various)

CD (2.78×10−10%)	182Yb 26Ne 24Ne

233Th	90	143	233.0415818(21)	21.83(4) min	β−	233Pa	1/2+

234Th	Uranium X1	90	144	234.043601(4)	24.10(3) d	β−	234mPa	0+	Trace

235Th	90	145	235.04751(5)	7.2(1) min	β−	235Pa	(1/2+)#

236Th	90	146	236.04987(21)#	37.5(2) min	β−	236Pa	0+

237Th	90	147	237.05389(39)#	4.8(5) min	β−	237Pa	5/2+#

238Th	90	148	238.0565(3)#	9.4(20) min	β−	238Pa	0+

Sentence(s)

228Th has a half-life of 1.9116 years.

final_sentence: 228Th has a half-life of 1.9116 years.