Thorium

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 Number90
Atomic Weight232.0377
Mass Number232
Group
Period7
Blockf
Protons90 p+
Neutrons142 n0
Electrons90 e-
Thorium sample 0.1g.jpg Animated Bohr Model of Th (Thorium) Enhanced Bohr Model of Th (Thorium) Bohr Model: Th (Thorium) Orbital Diagram of Th (Thorium)

Properties

Atomic Radius
180 pm
Molar Volume
Covalent Radius
175 pm
Metallic Radius
Ionic Radius
94 pm
Crystal Radius
108 pm
Van der Waals Radius
245 pm
Density
11.7 g/cm³
Energy
Proton Affinity
Electron Affinity
Ionization Energy
Heat of Vaporization
513.7 kJ/mol
Heat of Fusion
16.11 kJ/mol
Heat of Formation
602 kJ/mol
Electrons
Electron Shells2, 8, 18, 32, 18, 10, 2
Valence Electrons4
Electron Configuration[Rn] 6d2 7s2
Oxidation States-1, 1, 2, 3, 4
Electronegativity
1.3
Electrophilicity
Phases
PhaseSolid
Gas Phase
Boiling Point
5,058.15 K
Melting Point
2,023.15 K
Critical Pressure
Critical Temperature
Triple Point
Visual
Color
Silver
Appearancesilvery, 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
TypeConductor
Electrical Conductivity
6.7 MS/m
Electrical Resistivity
0.00000015 m Ω
Superconducting Point
1.38 K
Magnetism
Typeparamagnetic
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 StructureFace Centered Cubic (FCC)
Lattice Constant
5.08 Å
Lattice Anglesπ/2, π/2, π/2
Mechanical Properties
Hardness
3 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
CategoryActinides, Actinides
CAS Group
IUPAC Group
Glawe Number34
Mendeleev Number16
Pettifor Number47
Geochemical Classrare earth & related
Goldschmidt Classlitophile
Other
Gas Basicity
Dipole Polarizability
217 ± 54 a₀
C6 Dispersion Coefficient
Allotropes
Neutron Cross Section
7.4
Neutron Mass Absorption
0.001
Quantum Numbers3F2
Space Group225 (Fm_3m)

Isotopes of Thorium

Stable Isotopes2
Unstable Isotopes30
Radioactive Isotopes32

208Th

AbundanceRadioactive ☢️
Relative Atomic Mass
208.017915348 ± 0.000034208 Da
Mass Number208
G-Factor
0
Half Life
2.4 ± 1.2 ms
Spin0
Quadrupole Moment
0
Discovery Year2010
Parity+

208Th Decay Modes
Decay ModeIntensity
α (α emission)100%

209Th

AbundanceRadioactive ☢️
Relative Atomic Mass
209.017601 ± 0.000111 Da
Mass Number209
G-Factor
Half Life
Spin5/2
Quadrupole Moment
Discovery Year
Parity-

209Th Decay Modes
Decay ModeIntensity
α (α emission)%
β+ (β+ decay; β+ = ϵ + e+)%

210Th

AbundanceRadioactive ☢️
Relative Atomic Mass
210.015093515 ± 0.000020299 Da
Mass Number210
G-Factor
0
Half Life
16 ± 3.6 ms
Spin0
Quadrupole Moment
0
Discovery Year1995
Parity+

210Th Decay Modes
Decay ModeIntensity
α (α emission)100%
β+ (β+ decay; β+ = ϵ + e+)%

211Th

AbundanceRadioactive ☢️
Relative Atomic Mass
211.014896923 ± 0.000092399 Da
Mass Number211
G-Factor
Half Life
48 ± 20 ms
Spin5/2
Quadrupole Moment
Discovery Year1995
Parity-

211Th Decay Modes
Decay ModeIntensity
α (α emission)100%
β+ (β+ decay; β+ = ϵ + e+)%

212Th

AbundanceRadioactive ☢️
Relative Atomic Mass
212.01300157 ± 0.000010852 Da
Mass Number212
G-Factor
0
Half Life
31.7 ± 1.3 ms
Spin0
Quadrupole Moment
0
Discovery Year1980
Parity+

212Th Decay Modes
Decay ModeIntensity
α (α emission)100%
β+ (β+ decay; β+ = ϵ + e+)%

213Th

AbundanceRadioactive ☢️
Relative Atomic Mass
213.01301147 ± 0.000009895 Da
Mass Number213
G-Factor
Half Life
144 ± 21 ms
Spin5/2
Quadrupole Moment
Discovery Year1968
Parity-

213Th Decay Modes
Decay ModeIntensity
α (α emission)100%
β+ (β+ decay; β+ = ϵ + e+)%

214Th

AbundanceRadioactive ☢️
Relative Atomic Mass
214.01148148 ± 0.000011445 Da
Mass Number214
G-Factor
0
Half Life
87 ± 10 ms
Spin0
Quadrupole Moment
0
Discovery Year1968
Parity+

214Th Decay Modes
Decay ModeIntensity
α (α emission)100%
β+ (β+ decay; β+ = ϵ + e+)%

215Th

AbundanceRadioactive ☢️
Relative Atomic Mass
215.01172464 ± 0.0000068 Da
Mass Number215
G-Factor
Half Life
1.35 ± 0.14 s
Spin1/2
Quadrupole Moment
0
Discovery Year1968
Parity-

215Th Decay Modes
Decay ModeIntensity
α (α emission)100%

216Th

AbundanceRadioactive ☢️
Relative Atomic Mass
216.011055933 ± 0.00001192 Da
Mass Number216
G-Factor
0
Half Life
26.28 ± 0.16 ms
Spin0
Quadrupole Moment
0
Discovery Year1968
Parity+

216Th Decay Modes
Decay ModeIntensity
α (α emission)100%
β+ (β+ decay; β+ = ϵ + e+)%

217Th

AbundanceRadioactive ☢️
Relative Atomic Mass
217.013103443 ± 0.000011394 Da
Mass Number217
G-Factor
Half Life
248 ± 4 us
Spin9/2
Quadrupole Moment
Discovery Year1968
Parity+

217Th Decay Modes
Decay ModeIntensity
α (α emission)100%

218Th

AbundanceRadioactive ☢️
Relative Atomic Mass
218.013276248 ± 0.000011289 Da
Mass Number218
G-Factor
0
Half Life
122 ± 5 ns
Spin0
Quadrupole Moment
0
Discovery Year1973
Parity+

218Th Decay Modes
Decay ModeIntensity
α (α emission)100%

219Th

AbundanceRadioactive ☢️
Relative Atomic Mass
219.015526432 ± 0.000060611 Da
Mass Number219
G-Factor
Half Life
1.023 ± 0.018 us
Spin9/2
Quadrupole Moment
Discovery Year1973
Parity+

219Th Decay Modes
Decay ModeIntensity
α (α emission)100%
β+ (β+ decay; β+ = ϵ + e+)%

220Th

AbundanceRadioactive ☢️
Relative Atomic Mass
220.015769866 ± 0.000014693 Da
Mass Number220
G-Factor
0
Half Life
10.2 ± 0.3 us
Spin0
Quadrupole Moment
0
Discovery Year1973
Parity+

220Th Decay Modes
Decay ModeIntensity
α (α emission)100%
ϵ (electron capture)%

221Th

AbundanceRadioactive ☢️
Relative Atomic Mass
221.018185757 ± 0.000008582 Da
Mass Number221
G-Factor
Half Life
1.75 ± 0.02 ms
Spin7/2
Quadrupole Moment
Discovery Year1970
Parity+

221Th Decay Modes
Decay ModeIntensity
α (α emission)100%

222Th

AbundanceRadioactive ☢️
Relative Atomic Mass
222.01846822 ± 0.000010966 Da
Mass Number222
G-Factor
0
Half Life
2.24 ± 0.03 ms
Spin0
Quadrupole Moment
0
Discovery Year1970
Parity+

222Th Decay Modes
Decay ModeIntensity
α (α emission)100%
ϵ (electron capture)%

223Th

AbundanceRadioactive ☢️
Relative Atomic Mass
223.020811083 ± 0.000008527 Da
Mass Number223
G-Factor
Half Life
600 ± 20 ms
Spin5/2
Quadrupole Moment
Discovery Year1952
Parity

223Th Decay Modes
Decay ModeIntensity
α (α emission)100%

224Th

AbundanceRadioactive ☢️
Relative Atomic Mass
224.021466137 ± 0.00001031 Da
Mass Number224
G-Factor
0
Half Life
1.04 ± 0.02 s
Spin0
Quadrupole Moment
0
Discovery Year1949
Parity+

224Th Decay Modes
Decay ModeIntensity
α (α emission)100%
+ (double β+ decay)%

225Th

AbundanceRadioactive ☢️
Relative Atomic Mass
225.023950975 ± 0.000005467 Da
Mass Number225
G-Factor
Half Life
8.75 ± 0.04 m
Spin3/2
Quadrupole Moment
Discovery Year1949
Parity+

225Th Decay Modes
Decay ModeIntensity
α (α emission)90%
ϵ (electron capture)%

226Th

AbundanceRadioactive ☢️
Relative Atomic Mass
226.024903699 ± 0.00000481 Da
Mass Number226
G-Factor
0
Half Life
30.7 ± 0.03 m
Spin0
Quadrupole Moment
0
Discovery Year1948
Parity+

226Th Decay Modes
Decay ModeIntensity
α (α emission)100%
18O3.2%

227Th

AbundanceRadioactive ☢️
Relative Atomic Mass
227.027702546 ± 0.000002241 Da
Mass Number227
G-Factor
Half Life
18.693 ± 0.004 d
Spin1/2
Quadrupole Moment
0
Discovery Year1906
Parity+

227Th Decay Modes
Decay ModeIntensity
α (α emission)100%

228Th

AbundanceRadioactive ☢️
Relative Atomic Mass
228.028739741 ± 0.000001938 Da
Mass Number228
G-Factor
0
Half Life
1.9125 ± 0.0007 y
Spin0
Quadrupole Moment
0
Discovery Year1905
Parity+

228Th Decay Modes
Decay ModeIntensity
α (α emission)100%
20O1.13%

229Th

AbundanceRadioactive ☢️
Relative Atomic Mass
229.031761357 ± 0.000002581 Da
Mass Number229
G-Factor
0.184 ± 0.016
Half Life
7.916 ± 0.017 ky
Spin5/2
Quadrupole Moment
3.11 ± 0.06
Discovery Year1947
Parity+

229Th Decay Modes
Decay ModeIntensity
α (α emission)100%

230Th

AbundanceRadioactive ☢️
0.02 ± 0.02
Relative Atomic Mass
230.033132267 ± 0.000001297 Da
Mass Number230
G-Factor
0
Half Life
75.4 ± 0.3 ky
Spin0
Quadrupole Moment
0
Discovery Year1907
Parity+

230Th Decay Modes
Decay ModeIntensity
α (α emission)100%
SF (spontaneous fission)4%
24Ne (heavy cluster emission)5.8%

231Th

AbundanceRadioactive ☢️
Relative Atomic Mass
231.036302764 ± 0.000001306 Da
Mass Number231
G-Factor
Half Life
25.52 ± 0.01 h
Spin5/2
Quadrupole Moment
Discovery Year1911
Parity+

231Th Decay Modes
Decay ModeIntensity
β (β decay)100%

232Th

AbundanceRadioactive ☢️
99.98 ± 0.02
Relative Atomic Mass
232.038053606 ± 0.000001525 Da
Mass Number232
G-Factor
0
Half Life
14 ± 0.1 Gy
Spin0
Quadrupole Moment
0
Discovery Year1898
Parity+

232Th Decay Modes
Decay ModeIntensity
α (α emission)100%
SF (spontaneous fission)1.1%
26Ne2.78%
(double β decay)%

233Th

AbundanceRadioactive ☢️
Relative Atomic Mass
233.041580126 ± 0.000001528 Da
Mass Number233
G-Factor
Half Life
21.83 ± 0.04 m
Spin1/2
Quadrupole Moment
0
Discovery Year1935
Parity+

233Th Decay Modes
Decay ModeIntensity
β (β decay)100%

234Th

AbundanceRadioactive ☢️
Relative Atomic Mass
234.043599801 ± 0.000002779 Da
Mass Number234
G-Factor
0
Half Life
24.107 ± 0.024 d
Spin0
Quadrupole Moment
0
Discovery Year1900
Parity+

234Th Decay Modes
Decay ModeIntensity
β (β decay)100%
α (α emission)%

235Th

AbundanceRadioactive ☢️
Relative Atomic Mass
235.047255 ± 0.000014 Da
Mass Number235
G-Factor
Half Life
7.2 ± 0.1 m
Spin1/2
Quadrupole Moment
0
Discovery Year1969
Parity+

235Th Decay Modes
Decay ModeIntensity
β (β decay)100%

236Th

AbundanceRadioactive ☢️
Relative Atomic Mass
236.049657 ± 0.000015 Da
Mass Number236
G-Factor
0
Half Life
37.3 ± 1.5 m
Spin0
Quadrupole Moment
0
Discovery Year1973
Parity+

236Th Decay Modes
Decay ModeIntensity
β (β decay)100%

237Th

AbundanceRadioactive ☢️
Relative Atomic Mass
237.053629 ± 0.000017 Da
Mass Number237
G-Factor
Half Life
4.8 ± 0.5 m
Spin5/2
Quadrupole Moment
Discovery Year1993
Parity+

237Th Decay Modes
Decay ModeIntensity
β (β decay)100%

238Th

AbundanceRadioactive ☢️
Relative Atomic Mass
238.056388 ± 0.000304 Da
Mass Number238
G-Factor
0
Half Life
9.4 ± 2 m
Spin0
Quadrupole Moment
0
Discovery Year1999
Parity+

238Th Decay Modes
Decay ModeIntensity
β (β decay)100%

239Th

AbundanceRadioactive ☢️
Relative Atomic Mass
239.060655 ± 0.000429 Da
Mass Number239
G-Factor
Half Life
Spin7/2
Quadrupole Moment
Discovery Year
Parity+

239Th Decay Modes
Decay ModeIntensity
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

DiscoverersJöns Berzelius
Discovery LocationSweden
Discovery Year1828
Etymology (Name Origin)Named for Thor, Norse god of thunder.
PronunciationTHOR-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