Thorium (Th)

Grey radioactive metallic element. Belongs to actinoids. Found in monazite sand in Brazil, India and the US. Thorium-232 has a half-life of 1.39x10^10 years. Can be used as a nuclear fuel for breeder reactors. Thorium-232 captures slow Neutrons and breeds uranium-233. Discovered by Jons J. Berzelius in 1829.

Atomic Number	90
Atomic Weight	232.0377
Mass Number	232

Group
Period	7
Block	f

Protons	90 p⁺
Neutrons	142 n⁰
Electrons	90 e^-

Properties

Energy
Atomic Radius	180 pm 288 pm
Molar Volume	19.8 cm³/mol
Covalent Radius	175 pm 143 pm 136 pm 206 pm
Metallic Radius
Ionic Radius	94 pm 105 pm 109 pm 113 pm 118 pm 121 pm 120.9 pm
Crystal Radius	108 pm 119 pm 123 pm 127 pm 132 pm 135 pm 134.9 pm
Van der Waals Radius	240 pm 245 pm 274 pm 339.6 pm
Density	11.7 g/cm³
Proton Affinity
Electron Affinity
Ionization Energy	6.3067 eV/particle 11.9 eV/particle 18.32 eV/particle 28.648 eV/particle 58 eV/particle 69.1 eV/particle 82 eV/particle 95 eV/particle 118 eV/particle 133 eV/particle 165 eV/particle 181 eV/particle 262 eV/particle 285 eV/particle 310 eV/particle 336 eV/particle 362 eV/particle 389 eV/particle 424 eV/particle 451 eV/particle 480 eV/particle 508 eV/particle 650 eV/particle 680 eV/particle 720 eV/particle 750 eV/particle 830 eV/particle 900 eV/particle 970 eV/particle 1,010 eV/particle 1,090 eV/particle 1,160 eV/particle 1,240 eV/particle 1,310 eV/particle 1,380 eV/particle 1,460 eV/particle 1,530 eV/particle 1,600 eV/particle 1,680 eV/particle 1,760 eV/particle 1,830 eV/particle 1,910 eV/particle 2,000 eV/particle 2,060 eV/particle 2,390 eV/particle 2,455 eV/particle 2,524 eV/particle 2,598 eV/particle 2,669 eV/particle 2,737 eV/particle 2,860 eV/particle 2,935 eV/particle 3,013 eV/particle 3,086 eV/particle 3,375 eV/particle 3,445 eV/particle 3,522 eV/particle 3,593 eV/particle 3,943 eV/particle 4,025 eV/particle 4,230 eV/particle 4,313 eV/particle 6,972 eV/particle 7,130 eV/particle 7,299 eV/particle 7,480 eV/particle 7,650 eV/particle 7,820 eV/particle 8,180 eV/particle 8,350 eV/particle 8,550 eV/particle 8,720 eV/particle 9,220 eV/particle 9,370 eV/particle 9,540 eV/particle 9,690 eV/particle 10,790 eV/particle 10,970 eV/particle 11,340 eV/particle 11,510 eV/particle 24,060 eV/particle 24,480 eV/particle 24,940 eV/particle 25,360 eV/particle 29,410 eV/particle 29,970 eV/particle 30,680 eV/particle 31,122.8 eV/particle 123,086.4 eV/particle 125,253.4 eV/particle
Heat of Vaporization	513.7 kJ/mol
Heat of Fusion	16.11 kJ/mol
Heat of Formation	602 kJ/mol
Electrons
Electron Shells	2, 8, 18, 32, 18, 10, 2
Valence Electrons	4
Electron Configuration	[Rn] 6d² 7s²
Oxidation States	-1, 1, 2, 3, 4
Electronegativity	0.10277 1.3
Electrophilicity
Phases
Phase	Solid
Gas Phase
Boiling Point	5,058.15 K
Melting Point	2,023.15 K
Critical Pressure
Critical Temperature
Triple Point
Visual
Color	Silver #ff1493 #00baff #00baff
Appearance	silvery, often with black tarnish
Refractive Index
Thermodynamic Properties
Thermal Conductivity
Thermal Expansion	0.000011 1/K
Molar Heat Capacity	27.32 J/(mol K)
Specific Heat Capacity	0.118 J/(g⋅K)
Heat Capacity Ratio (Adiabatic Index)
Electrical Properties
Type	Conductor
Electrical Conductivity	6.7 MS/m
Electrical Resistivity	0.00000015 m Ω
Superconducting Point	1.38 K
Magnetism
Type	paramagnetic
Magnetic Susceptibility (Mass)	0.0000000072 m³/Kg
Magnetic Susceptibility (Molar)	0.0000000017 m³/mol
Magnetic Susceptibility (Volume)	0.000084
Magnetic Ordering
Curie Point
Neel Point
Structure
Crystal Structure	Face Centered Cubic (FCC)
Lattice Constant	5.08 Å
Lattice Angles	π/2, π/2, π/2
Mechanical Properties
Hardness	400 MPa 3 MPa 350 MPa
Bulk Modulus	54 GPa
Shear Modulus	31 GPa
Young Modulus	79 GPa
Poisson Ratio	0.27
Speed of Sound	2,490 m/s
Classification
Category	Actinides, Actinides
CAS Group
IUPAC Group
Glawe Number	34
Mendeleev Number	16
Pettifor Number	47
Geochemical Class	rare earth & related
Goldschmidt Class	litophile
Other
Gas Basicity
Dipole Polarizability	217 ± 54 a₀
C6 Dispersion Coefficient
Allotropes
Neutron Cross Section	7.4
Neutron Mass Absorption	0.001
Quantum Numbers	3F2
Space Group	225 (Fm_3m)

Isotopes of Thorium

Stable Isotopes	2
Unstable Isotopes	30
Radioactive Isotopes	32

²⁰⁸Th

Abundance	Radioactive ☢️
Relative Atomic Mass	208.017915348 ± 0.000034208 Da
Mass Number	208
G-Factor	0
Half Life	2.4 ± 1.2 ms
Spin	0
Quadrupole Moment	0
Discovery Year	2010
Parity	+

²⁰⁸Th Decay Modes

Decay Mode	Intensity
α (α emission)	100%

²⁰⁹Th

Abundance	Radioactive ☢️
Relative Atomic Mass	209.017601 ± 0.000111 Da
Mass Number	209
G-Factor
Half Life
Spin	5/2
Quadrupole Moment
Discovery Year
Parity	-

²⁰⁹Th Decay Modes

Decay Mode	Intensity
α (α emission)	%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	%

²¹⁰Th

Abundance	Radioactive ☢️
Relative Atomic Mass	210.015093515 ± 0.000020299 Da
Mass Number	210
G-Factor	0
Half Life	16 ± 3.6 ms
Spin	0
Quadrupole Moment	0
Discovery Year	1995
Parity	+

²¹⁰Th Decay Modes

Decay Mode	Intensity
α (α emission)	100%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	%

²¹¹Th

Abundance	Radioactive ☢️
Relative Atomic Mass	211.014896923 ± 0.000092399 Da
Mass Number	211
G-Factor
Half Life	48 ± 20 ms
Spin	5/2
Quadrupole Moment
Discovery Year	1995
Parity	-

²¹¹Th Decay Modes

Decay Mode	Intensity
α (α emission)	100%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	%

²¹²Th

Abundance	Radioactive ☢️
Relative Atomic Mass	212.01300157 ± 0.000010852 Da
Mass Number	212
G-Factor	0
Half Life	31.7 ± 1.3 ms
Spin	0
Quadrupole Moment	0
Discovery Year	1980
Parity	+

²¹²Th Decay Modes

Decay Mode	Intensity
α (α emission)	100%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	%

²¹³Th

Abundance	Radioactive ☢️
Relative Atomic Mass	213.01301147 ± 0.000009895 Da
Mass Number	213
G-Factor
Half Life	144 ± 21 ms
Spin	5/2
Quadrupole Moment
Discovery Year	1968
Parity	-

²¹³Th Decay Modes

Decay Mode	Intensity
α (α emission)	100%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	%

²¹⁴Th

Abundance	Radioactive ☢️
Relative Atomic Mass	214.01148148 ± 0.000011445 Da
Mass Number	214
G-Factor	0
Half Life	87 ± 10 ms
Spin	0
Quadrupole Moment	0
Discovery Year	1968
Parity	+

²¹⁴Th Decay Modes

Decay Mode	Intensity
α (α emission)	100%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	%

²¹⁵Th

Abundance	Radioactive ☢️
Relative Atomic Mass	215.01172464 ± 0.0000068 Da
Mass Number	215
G-Factor
Half Life	1.35 ± 0.14 s
Spin	1/2
Quadrupole Moment	0
Discovery Year	1968
Parity	-

²¹⁵Th Decay Modes

Decay Mode	Intensity
α (α emission)	100%

²¹⁶Th

Abundance	Radioactive ☢️
Relative Atomic Mass	216.011055933 ± 0.00001192 Da
Mass Number	216
G-Factor	0
Half Life	26.28 ± 0.16 ms
Spin	0
Quadrupole Moment	0
Discovery Year	1968
Parity	+

²¹⁶Th Decay Modes

Decay Mode	Intensity
α (α emission)	100%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	%

²¹⁷Th

Abundance	Radioactive ☢️
Relative Atomic Mass	217.013103443 ± 0.000011394 Da
Mass Number	217
G-Factor
Half Life	248 ± 4 us
Spin	9/2
Quadrupole Moment
Discovery Year	1968
Parity	+

²¹⁷Th Decay Modes

Decay Mode	Intensity
α (α emission)	100%

²¹⁸Th

Abundance	Radioactive ☢️
Relative Atomic Mass	218.013276248 ± 0.000011289 Da
Mass Number	218
G-Factor	0
Half Life	122 ± 5 ns
Spin	0
Quadrupole Moment	0
Discovery Year	1973
Parity	+

²¹⁸Th Decay Modes

Decay Mode	Intensity
α (α emission)	100%

²¹⁹Th

Abundance	Radioactive ☢️
Relative Atomic Mass	219.015526432 ± 0.000060611 Da
Mass Number	219
G-Factor
Half Life	1.023 ± 0.018 us
Spin	9/2
Quadrupole Moment
Discovery Year	1973
Parity	+

²¹⁹Th Decay Modes

Decay Mode	Intensity
α (α emission)	100%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	%

²²⁰Th

Abundance	Radioactive ☢️
Relative Atomic Mass	220.015769866 ± 0.000014693 Da
Mass Number	220
G-Factor	0
Half Life	10.2 ± 0.3 us
Spin	0
Quadrupole Moment	0
Discovery Year	1973
Parity	+

²²⁰Th Decay Modes

Decay Mode	Intensity
α (α emission)	100%
ϵ (electron capture)	%

²²¹Th

Abundance	Radioactive ☢️
Relative Atomic Mass	221.018185757 ± 0.000008582 Da
Mass Number	221
G-Factor
Half Life	1.75 ± 0.02 ms
Spin	7/2
Quadrupole Moment
Discovery Year	1970
Parity	+

²²¹Th Decay Modes

Decay Mode	Intensity
α (α emission)	100%

²²²Th

Abundance	Radioactive ☢️
Relative Atomic Mass	222.01846822 ± 0.000010966 Da
Mass Number	222
G-Factor	0
Half Life	2.24 ± 0.03 ms
Spin	0
Quadrupole Moment	0
Discovery Year	1970
Parity	+

²²²Th Decay Modes

Decay Mode	Intensity
α (α emission)	100%
ϵ (electron capture)	%

²²³Th

Abundance	Radioactive ☢️
Relative Atomic Mass	223.020811083 ± 0.000008527 Da
Mass Number	223
G-Factor
Half Life	600 ± 20 ms
Spin	5/2
Quadrupole Moment
Discovery Year	1952
Parity

²²³Th Decay Modes

Decay Mode	Intensity
α (α emission)	100%

²²⁴Th

Abundance	Radioactive ☢️
Relative Atomic Mass	224.021466137 ± 0.00001031 Da
Mass Number	224
G-Factor	0
Half Life	1.04 ± 0.02 s
Spin	0
Quadrupole Moment	0
Discovery Year	1949
Parity	+

²²⁴Th Decay Modes

Decay Mode	Intensity
α (α emission)	100%
2β⁺ (double β⁺ decay)	%

²²⁵Th

Abundance	Radioactive ☢️
Relative Atomic Mass	225.023950975 ± 0.000005467 Da
Mass Number	225
G-Factor
Half Life	8.75 ± 0.04 m
Spin	3/2
Quadrupole Moment
Discovery Year	1949
Parity	+

²²⁵Th Decay Modes

Decay Mode	Intensity
α (α emission)	90%
ϵ (electron capture)	%

²²⁶Th

Abundance	Radioactive ☢️
Relative Atomic Mass	226.024903699 ± 0.00000481 Da
Mass Number	226
G-Factor	0
Half Life	30.7 ± 0.03 m
Spin	0
Quadrupole Moment	0
Discovery Year	1948
Parity	+

²²⁶Th Decay Modes

Decay Mode	Intensity
α (α emission)	100%
18O	3.2%

²²⁷Th

Abundance	Radioactive ☢️
Relative Atomic Mass	227.027702546 ± 0.000002241 Da
Mass Number	227
G-Factor
Half Life	18.693 ± 0.004 d
Spin	1/2
Quadrupole Moment	0
Discovery Year	1906
Parity	+

²²⁷Th Decay Modes

Decay Mode	Intensity
α (α emission)	100%

²²⁸Th

Abundance	Radioactive ☢️
Relative Atomic Mass	228.028739741 ± 0.000001938 Da
Mass Number	228
G-Factor	0
Half Life	1.9125 ± 0.0007 y
Spin	0
Quadrupole Moment	0
Discovery Year	1905
Parity	+

²²⁸Th Decay Modes

Decay Mode	Intensity
α (α emission)	100%
20O	1.13%

²²⁹Th

Abundance	Radioactive ☢️
Relative Atomic Mass	229.031761357 ± 0.000002581 Da
Mass Number	229
G-Factor	0.184 ± 0.016
Half Life	7.916 ± 0.017 ky
Spin	5/2
Quadrupole Moment	3.11 ± 0.06
Discovery Year	1947
Parity	+

²²⁹Th Decay Modes

Decay Mode	Intensity
α (α emission)	100%

²³⁰Th

Abundance	Radioactive ☢️ 0.02 ± 0.02
Relative Atomic Mass	230.033132267 ± 0.000001297 Da
Mass Number	230
G-Factor	0
Half Life	75.4 ± 0.3 ky
Spin	0
Quadrupole Moment	0
Discovery Year	1907
Parity	+

²³⁰Th Decay Modes

Decay Mode	Intensity
α (α emission)	100%
SF (spontaneous fission)	4%
24Ne (heavy cluster emission)	5.8%

²³¹Th

Abundance	Radioactive ☢️
Relative Atomic Mass	231.036302764 ± 0.000001306 Da
Mass Number	231
G-Factor
Half Life	25.52 ± 0.01 h
Spin	5/2
Quadrupole Moment
Discovery Year	1911
Parity	+

²³¹Th Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

²³²Th

Abundance	Radioactive ☢️ 99.98 ± 0.02
Relative Atomic Mass	232.038053606 ± 0.000001525 Da
Mass Number	232
G-Factor	0
Half Life	14 ± 0.1 Gy
Spin	0
Quadrupole Moment	0
Discovery Year	1898
Parity	+

²³²Th Decay Modes

Decay Mode	Intensity
α (α emission)	100%
SF (spontaneous fission)	1.1%
26Ne	2.78%
2β⁻ (double β⁻ decay)	%

²³³Th

Abundance	Radioactive ☢️
Relative Atomic Mass	233.041580126 ± 0.000001528 Da
Mass Number	233
G-Factor
Half Life	21.83 ± 0.04 m
Spin	1/2
Quadrupole Moment	0
Discovery Year	1935
Parity	+

²³³Th Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

²³⁴Th

Abundance	Radioactive ☢️
Relative Atomic Mass	234.043599801 ± 0.000002779 Da
Mass Number	234
G-Factor	0
Half Life	24.107 ± 0.024 d
Spin	0
Quadrupole Moment	0
Discovery Year	1900
Parity	+

²³⁴Th Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
α (α emission)	%

²³⁵Th

Abundance	Radioactive ☢️
Relative Atomic Mass	235.047255 ± 0.000014 Da
Mass Number	235
G-Factor
Half Life	7.2 ± 0.1 m
Spin	1/2
Quadrupole Moment	0
Discovery Year	1969
Parity	+

²³⁵Th Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

²³⁶Th

Abundance	Radioactive ☢️
Relative Atomic Mass	236.049657 ± 0.000015 Da
Mass Number	236
G-Factor	0
Half Life	37.3 ± 1.5 m
Spin	0
Quadrupole Moment	0
Discovery Year	1973
Parity	+

²³⁶Th Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

²³⁷Th

Abundance	Radioactive ☢️
Relative Atomic Mass	237.053629 ± 0.000017 Da
Mass Number	237
G-Factor
Half Life	4.8 ± 0.5 m
Spin	5/2
Quadrupole Moment
Discovery Year	1993
Parity	+

²³⁷Th Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

²³⁸Th

Abundance	Radioactive ☢️
Relative Atomic Mass	238.056388 ± 0.000304 Da
Mass Number	238
G-Factor	0
Half Life	9.4 ± 2 m
Spin	0
Quadrupole Moment	0
Discovery Year	1999
Parity	+

²³⁸Th Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

²³⁹Th

Abundance	Radioactive ☢️
Relative Atomic Mass	239.060655 ± 0.000429 Da
Mass Number	239
G-Factor
Half Life
Spin	7/2
Quadrupole Moment
Discovery Year
Parity	+

²³⁹Th Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	%

History

Thorium was discovered by Jöns Jacob Berzelius in 1828, in Stockholm, Sweden. Thorium was first observed to be radioactive in 1898, independently, by Polish-French physicist Marie Curie and German chemist Gerhard Carl Schmidt. The crystal bar process was discovered by Anton Eduard van Arkel and Jan Hendrik de Boer in 1925 to produce high-purity metallic thorium. Named after Thor, Scandinavian god of war

Discoverers	Jöns Berzelius
Discovery Location	Sweden
Discovery Year	1828
Etymology (Name Origin)	Named for Thor, Norse god of thunder.
Pronunciation	THOR-i-em (English)

Thorium is highly radioactive

Thorium fuel research is continuing in several countries including the USA and India

Uses

Thorium is used to coat tungsten filaments in light bulbs. It is also used in its oxide form in gas tungsten arc welding to increase the high-temperature strength of tungsten electrodes and improve arc stability. Thorium-magnesium alloys are used in the aerospace industry for aircraft engines. Used in making strong alloys. Also in ultraviolet photoelectric cells. It is a common ingredient in high-quality lenses. Bombarded with neutrons make uranium-233, a nuclear fuel.

Sources

Found in various minerals like monazite and thorite.

Abundance
Abundance in Earth's crust	9.6 mg/kg
Abundance in Oceans	0.000001 mg/L
Abundance in Human Body	0 %
Abundance in Meteor	0.0000039 %
Abundance in Sun	0.00000003 %
Abundance in Universe	0.00000004 %

Nuclear Screening Constants

Thorium on ChemicalAid

Art & Architecture Thesaurus ID	300379770
Australian Educational Vocabulary ID	scot/3585
BNCF Thesaurus ID	37628
Bibliothèque nationale de France ID	11977429t
CAB ID	7540
CAS Registry Number	7440-29-1
ChEBI ID	33385
DSSTOX compound identifier	DTXCID6029759
DSSTox substance ID	DTXSID6049800
Den Store Danske ID	thorium
ECHA Substance Infocard ID	100.028.308
Encyclopædia Britannica Online ID	science/thorium
Encyclopædia Britannica Online ID	topic/helium-uranium-thorium-dating
Encyclopædia Universalis ID	thorium
Freebase ID	/m/025sk62
GND ID	4185331-3
Gran Enciclopèdia Catalana ID	0239406
Gran Enciclopèdia Catalana ID	0146927
Great Russian Encyclopedia Online ID	4198022
HSDB ID	864
Human Metabolome Database ID	HMDB0029215
ICSC ID	0337
InChI	InChI=1S/Th
InChIKey	ZSLUVFAKFWKJRC-UHFFFAOYSA-N
KBpedia ID	Thorium
KEGG ID	C19157
LEM ID	LEM201013005
Library of Congress authority ID	sh85134957
MeSH descriptor ID	D013910
NKCR AUT ID	ph543054
National Diet Library ID	00573342
National Library of Israel J9U ID	987007534013905171
OmegaWiki Defined Meaning	365213
OpenAlex ID	C527038400
PSH ID	5764
Quora topic ID	Thorium
RxNorm ID	1534769
Römpp online ID	RD-20-01588
Store medisinske leksikon ID	thorium
Store norske leksikon ID	thorium
Treccani ID	torio
UK Archival Thesaurus ID	f2/mt225/4347/5019
UK Parliament thesaurus ID	430967
UNESCO Thesaurus ID	concept14024
UNII	60YU5MIG9W
WordNet 3.1 Synset ID	14682288-n
YSO ID	21744

Thorium (Th)

Properties

Isotopes of Thorium

208Th

208Th Decay Modes

209Th

209Th Decay Modes

210Th

210Th Decay Modes

211Th

211Th Decay Modes

212Th

212Th Decay Modes

213Th

213Th Decay Modes

214Th

214Th Decay Modes

215Th

215Th Decay Modes

216Th

216Th Decay Modes

217Th

217Th Decay Modes

218Th

218Th Decay Modes

219Th

219Th Decay Modes

220Th

220Th Decay Modes

221Th

221Th Decay Modes

222Th

222Th Decay Modes

223Th

223Th Decay Modes

224Th

224Th Decay Modes

225Th

225Th Decay Modes

226Th

226Th Decay Modes

227Th

227Th Decay Modes

228Th

228Th Decay Modes

229Th

229Th Decay Modes

230Th

230Th Decay Modes

231Th

231Th Decay Modes

232Th

232Th Decay Modes

233Th

233Th Decay Modes

234Th

234Th Decay Modes

235Th

235Th Decay Modes

236Th

236Th Decay Modes

237Th

237Th Decay Modes

238Th

238Th Decay Modes

239Th

239Th Decay Modes