Isotopes of thorium
Encyclopedia
Although thorium
(Th) has 6 naturally occurring isotope
s, none of these isotopes are stable; however, one isotope, 232Th, is relatively stable, with a half-life of 14.05 billion years, considerably longer than the age of the earth
, and even slightly longer than the generally-accepted age of the universe
. This isotope makes up nearly all natural thorium. As such, thorium is considered to be mononuclidic
. It has a characteristic terrestrial isotopic composition and thus an atomic mass can be given.
Thirty radioisotopes have been characterized, with the most stable (after 232Th) being 230Th with a half-life of 75,380 years, 229Th with a half-life of 7,340 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, recently measured to be 7.6 ± 0.5 eV.
The known isotopes of thorium range in mass number
from 209 to 238.
of thorium
which has 138 neutrons. It was once named Radiothorium, due to its occurrence in the disintegration chain of thorium-232. It has a half-life
of 1.9116 years. It undergoes alpha decay
to 224Ra
. Occasionally it decays by the unusual route of cluster decay
, emitting a nucleus of 20O
and producing stable 208Pb
. It is a parent isotope of 232U
Th-228 has an atomic weight of 228.0287411 grams/mole. Uranium-232 decays to this nuclide by alpha emission.
of thorium
that decays by alpha
emission with a half-life
of 7340 years.
229Th is produced by the decay of uranium-233
, and its principal use is for the production of the medical isotopes
actinium-225 and bismuth-213.
with a remarkably low excitation energy. This would make it the lowest-energy nuclear isomer known, and it might be possible to excite this nuclear state using laser
s with wavelengths in the vacuum ultraviolet.The isomer might have application for high density energy storage, an accurate clock, as a qubit
for quantum computing, or to test the effect of the chemical environment on nuclear decay rates.
The half-life of this excited state is not known, though it is estimated at 5 hours. If this isomer were to decay it would produce a gamma ray
(defined by its origin not its wavelength) in the ultraviolet range.
For several years, the accepted energy of the state was 3.5 eV, with an uncertainty of 1.0 eV.
These "ultraviolet gamma rays" were thought to have been detected at one time, but this observation has since been found to be from nitrogen gas excited by higher energy emissions.
Recent measurements of higher-energy gamma rays give 7.6 eV as the energy of the 3/2+ state, with an uncertainty of 0.5 eV.
of thorium
which can be used to date coral
s and determine ocean current
flux. Ionium was a name given early in the study of radioactive elements to the 230Th isotope
produced in the decay chain
of 238U
before it was realized that ionium and thorium
are chemically identical. The symbol Io was used for this supposed element.
. It is found in very small amounts on the earth
and has a half-life
of 25.5 hours. When it decays it emits a beta ray and forms protactinium-231. It has a decay energy of 0.39 MeV. It has a mass of 231.0363043 grams/mole.
, the main article on thorium
effectively discusses this isotope.
232Th is the only primordial isotope of thorium
and makes up effectively all of natural thorium, with other isotopes of thorium appearing only in trace amounts as relatively short-lived decay product
s of uranium
and thorium.
232Th decays by alpha decay
with a half-life
of 1.405 years, over three times the age of the earth
. Its decay chain
is the thorium series eventually ending in lead-208. The remainder of the chain is quick; the longest half-lives in it are 5.75 years for radium-228 and 1.91 years for thorium-228, with all other half-lives totaling less than 5 days.
232Th is a fertile material
able to absorb
a neutron
and undergo transmutation
into the fissile
nuclide
uranium-233
, which is the basis of the thorium fuel cycle
.
In the form of Thorotrast
, a thorium dioxide
suspension
, it was used as contrast medium
in early X-ray
diagnostics. Thorium-232 is now classified as carcinogen
ic.
that decays into protactinium-233 through beta decay. It has a half-life of 21.83 minutes.
of thorium
whose nuclei
contain 144 neutron
s. Th-234 has a half-life
of about 24.1 days, and when it decays, it emits a beta particle
, and in so doing, it transmutes into protactinium
-234. Th-234 has a mass of about 234.0436 atomic mass unit
s (amu
), and it has a decay energy of about 270 KeV (kiloelectron-volts). Uranium
-238 usually decays into this isotope of thorium. (It can undergo spontaneous fission
.)
Thorium
Thorium is a natural radioactive chemical element with the symbol Th and atomic number 90. It was discovered in 1828 and named after Thor, the Norse god of thunder....
(Th) has 6 naturally occurring isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
s, none of these isotopes are stable; however, one isotope, 232Th, is relatively stable, with a half-life of 14.05 billion years, considerably longer than the age of the earth
Age of the Earth
The age of the Earth is 4.54 billion years This age is based on evidence from radiometric age dating of meteorite material and is consistent with the ages of the oldest-known terrestrial and lunar samples...
, and even slightly longer than the generally-accepted age of the universe
Age of the universe
The age of the universe is the time elapsed since the Big Bang posited by the most widely accepted scientific model of cosmology. The best current estimate of the age of the universe is 13.75 ± 0.13 billion years within the Lambda-CDM concordance model...
. This isotope makes up nearly all natural thorium. As such, thorium is considered to be mononuclidic
Mononuclidic elements
A mononuclidic element is one of the 22 chemical elements that is found naturally on Earth essentially as a single nuclide . This single nuclide will have a characteristic atomic mass. Thus, the element's natural isotopic abundance is dominated either by one stable isotope or by one very long-lived...
. It has a characteristic terrestrial isotopic composition and thus an atomic mass can be given.
- Standard atomic mass: 232.03806(2) u
Thirty radioisotopes have been characterized, with the most stable (after 232Th) being 230Th with a half-life of 75,380 years, 229Th with a half-life of 7,340 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
Nuclear isomer
A nuclear isomer is a metastable state of an atomic nucleus caused by the excitation of one or more of its nucleons . "Metastable" refers to the fact that these excited states have half-lives more than 100 to 1000 times the half-lives of the other possible excited nuclear states...
(or metastable state) with a remarkably low excitation energy, recently measured to be 7.6 ± 0.5 eV.
The known isotopes of thorium range in mass number
Mass number
The mass number , also called atomic mass number or nucleon number, is the total number of protons and neutrons in an atomic nucleus. Because protons and neutrons both are baryons, the mass number A is identical with the baryon number B as of the nucleus as of the whole atom or ion...
from 209 to 238.
Thorium-228
228Th is an isotopeIsotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
of thorium
Thorium
Thorium is a natural radioactive chemical element with the symbol Th and atomic number 90. It was discovered in 1828 and named after Thor, the Norse god of thunder....
which has 138 neutrons. It was once named Radiothorium, due to its occurrence in the disintegration chain of thorium-232. It has a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of 1.9116 years. It undergoes alpha decay
Alpha decay
Alpha decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle and thereby transforms into an atom with a mass number 4 less and atomic number 2 less...
to 224Ra
Isotopes of radium
Radium has no stable or nearly stable isotopes, and thus a standard atomic mass cannot be given. The longest lived, and most common, isotope of radium is 226Ra with a half-life of 1600 years...
. Occasionally it decays by the unusual route of cluster decay
Cluster decay
Cluster decay is a type of nuclear decay in which a parent atomic nucleus with A nucleons and Z protons emits a cluster of Ne neutrons and Ze protons heavier than an alpha particle but lighter than a typical binary fission fragment Cluster decay (also named heavy particle radioactivity or heavy...
, emitting a nucleus of 20O
Isotopes of oxygen
There are three stable isotopes of oxygen that lead to oxygen having a standard atomic mass of 15.9994 u. 17 radioactive isotopes have also been characterized, with mass numbers from 12O to 28O, all short-lived, with the longest-lived being 15O with a half-life of 122.24 seconds...
and producing stable 208Pb
Isotopes of lead
Lead has four stable isotopes: 204Pb, 206Pb, 207Pb, 208Pb. Lead-204 is entirely a primordial nuclide and is not a radiogenic nuclide. The three isotopes lead-206, lead-207, and lead-208 represent the ends of three decay chains called the uranium series , the actinium series, and the thorium...
. It is a parent isotope of 232U
Th-228 has an atomic weight of 228.0287411 grams/mole. Uranium-232 decays to this nuclide by alpha emission.
Thorium-229
229Th is a radioactive isotopeIsotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
of thorium
Thorium
Thorium is a natural radioactive chemical element with the symbol Th and atomic number 90. It was discovered in 1828 and named after Thor, the Norse god of thunder....
that decays by alpha
Alpha particle
Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus, which is classically produced in the process of alpha decay, but may be produced also in other ways and given the same name...
emission with a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of 7340 years.
229Th is produced by the decay of uranium-233
Uranium-233
Uranium-233 is a fissile isotope of uranium, bred from Thorium as part of the thorium fuel cycle. It has been used in a few nuclear reactors and has been proposed for much wider use as a nuclear fuel. It has a half-life of 160,000 years....
, and its principal use is for the production of the medical isotopes
Nuclear medicine
In nuclear medicine procedures, elemental radionuclides are combined with other elements to form chemical compounds, or else combined with existing pharmaceutical compounds, to form radiopharmaceuticals. These radiopharmaceuticals, once administered to the patient, can localize to specific organs...
actinium-225 and bismuth-213.
Thorium-229m
Gamma ray spectroscopy has indicated that 229Th has a nuclear isomerNuclear isomer
A nuclear isomer is a metastable state of an atomic nucleus caused by the excitation of one or more of its nucleons . "Metastable" refers to the fact that these excited states have half-lives more than 100 to 1000 times the half-lives of the other possible excited nuclear states...
with a remarkably low excitation energy. This would make it the lowest-energy nuclear isomer known, and it might be possible to excite this nuclear state using laser
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
s with wavelengths in the vacuum ultraviolet.The isomer might have application for high density energy storage, an accurate clock, as a qubit
Qubit
In quantum computing, a qubit or quantum bit is a unit of quantum information—the quantum analogue of the classical bit—with additional dimensions associated to the quantum properties of a physical atom....
for quantum computing, or to test the effect of the chemical environment on nuclear decay rates.
The half-life of this excited state is not known, though it is estimated at 5 hours. If this isomer were to decay it would produce a gamma ray
Gamma ray
Gamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...
(defined by its origin not its wavelength) in the ultraviolet range.
For several years, the accepted energy of the state was 3.5 eV, with an uncertainty of 1.0 eV.
These "ultraviolet gamma rays" were thought to have been detected at one time, but this observation has since been found to be from nitrogen gas excited by higher energy emissions.
Recent measurements of higher-energy gamma rays give 7.6 eV as the energy of the 3/2+ state, with an uncertainty of 0.5 eV.
Thorium-230
230Th is a radioactive isotopeIsotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
of thorium
Thorium
Thorium is a natural radioactive chemical element with the symbol Th and atomic number 90. It was discovered in 1828 and named after Thor, the Norse god of thunder....
which can be used to date coral
Coral
Corals are marine animals in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.A coral "head" is a colony of...
s and determine ocean current
Ocean current
An ocean current is a continuous, directed movement of ocean water generated by the forces acting upon this mean flow, such as breaking waves, wind, Coriolis effect, cabbeling, temperature and salinity differences and tides caused by the gravitational pull of the Moon and the Sun...
flux. Ionium was a name given early in the study of radioactive elements to the 230Th isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
produced in the decay chain
Decay chain
In nuclear science, the decay chain refers to the radioactive decay of different discrete radioactive decay products as a chained series of transformations...
of 238U
Uranium-238
Uranium-238 is the most common isotope of uranium found in nature. It is not fissile, but is a fertile material: it can capture a slow neutron and after two beta decays become fissile plutonium-239...
before it was realized that ionium and thorium
Thorium
Thorium is a natural radioactive chemical element with the symbol Th and atomic number 90. It was discovered in 1828 and named after Thor, the Norse god of thunder....
are chemically identical. The symbol Io was used for this supposed element.
Thorium-231
231Th has 141 neutrons. It is the decay product of uranium-235Uranium-235
- References :* .* DOE Fundamentals handbook: Nuclear Physics and Reactor theory , .* A piece of U-235 the size of a grain of rice can produce energy equal to that contained in three tons of coal or fourteen barrels of oil. -External links:* * * one of the earliest articles on U-235 for the...
. It is found in very small amounts on the earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
and has a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of 25.5 hours. When it decays it emits a beta ray and forms protactinium-231. It has a decay energy of 0.39 MeV. It has a mass of 231.0363043 grams/mole.
Thorium-232
As Thorium is mononuclidicMononuclidic elements
A mononuclidic element is one of the 22 chemical elements that is found naturally on Earth essentially as a single nuclide . This single nuclide will have a characteristic atomic mass. Thus, the element's natural isotopic abundance is dominated either by one stable isotope or by one very long-lived...
, the main article on thorium
Thorium
Thorium is a natural radioactive chemical element with the symbol Th and atomic number 90. It was discovered in 1828 and named after Thor, the Norse god of thunder....
effectively discusses this isotope.
232Th is the only primordial isotope of thorium
Thorium
Thorium is a natural radioactive chemical element with the symbol Th and atomic number 90. It was discovered in 1828 and named after Thor, the Norse god of thunder....
and makes up effectively all of natural thorium, with other isotopes of thorium appearing only in trace amounts as relatively short-lived decay product
Decay product
In nuclear physics, a decay product is the remaining nuclide left over from radioactive decay. Radioactive decay often involves a sequence of steps...
s of uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
and thorium.
232Th decays by alpha decay
Alpha decay
Alpha decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle and thereby transforms into an atom with a mass number 4 less and atomic number 2 less...
with a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of 1.405 years, over three times the age of the earth
Age of the Earth
The age of the Earth is 4.54 billion years This age is based on evidence from radiometric age dating of meteorite material and is consistent with the ages of the oldest-known terrestrial and lunar samples...
. Its decay chain
Decay chain
In nuclear science, the decay chain refers to the radioactive decay of different discrete radioactive decay products as a chained series of transformations...
is the thorium series eventually ending in lead-208. The remainder of the chain is quick; the longest half-lives in it are 5.75 years for radium-228 and 1.91 years for thorium-228, with all other half-lives totaling less than 5 days.
232Th is a fertile material
Fertile material
Fertile material is a term used to describe nuclides which generally themselves do not undergo induced fission but from which fissile material is generated by neutron absorption and subsequent nuclei conversions...
able to absorb
Neutron capture
Neutron capture is a kind of nuclear reaction in which an atomic nucleus collides with one or more neutrons and they merge to form a heavier nucleus. Since neutrons have no electric charge they can enter a nucleus more easily than positively charged protons, which are repelled...
a neutron
Neutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
and undergo transmutation
Nuclear transmutation
Nuclear transmutation is the conversion of one chemical element or isotope into another. In other words, atoms of one element can be changed into atoms of other element by 'transmutation'...
into the fissile
Fissile
In nuclear engineering, a fissile material is one that is capable of sustaining a chain reaction of nuclear fission. By definition, fissile materials can sustain a chain reaction with neutrons of any energy. The predominant neutron energy may be typified by either slow neutrons or fast neutrons...
nuclide
Nuclide
A nuclide is an atomic species characterized by the specific constitution of its nucleus, i.e., by its number of protons Z, its number of neutrons N, and its nuclear energy state....
uranium-233
Uranium-233
Uranium-233 is a fissile isotope of uranium, bred from Thorium as part of the thorium fuel cycle. It has been used in a few nuclear reactors and has been proposed for much wider use as a nuclear fuel. It has a half-life of 160,000 years....
, which is the basis of the thorium fuel cycle
Thorium fuel cycle
The thorium fuel cycle is a nuclear fuel cycle that uses the naturally abundant isotope of thorium, , as the fertile material. In the reactor, is transmuted into the fissile artificial uranium isotope which is the nuclear fuel. Unlike natural uranium, natural thorium contains only trace amounts...
.
In the form of Thorotrast
Thorotrast
Thorotrast is a suspension containing particles of the radioactive compound thorium dioxide, ThO2, used as a contrast medium in X-ray diagnostics in the 1930s and 40s ....
, a thorium dioxide
Thorium dioxide
Thorium dioxide , also called thorium oxide is a white, crystalline powder. It was formerly known as thoria or thorina. It is produced mainly as a by-product of lanthanide and uranium production.[1]...
suspension
Suspension (chemistry)
In chemistry, a suspension is a heterogeneous fluid containing solid particles that are sufficiently large for sedimentation. Usually they must be larger than 1 micrometer. The internal phase is dispersed throughout the external phase through mechanical agitation, with the use of certain...
, it was used as contrast medium
Contrast medium
A medical contrast medium is a substance used to enhance the contrast of structures or fluids within the body in medical imaging...
in early X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
diagnostics. Thorium-232 is now classified as carcinogen
Carcinogen
A carcinogen is any substance, radionuclide, or radiation that is an agent directly involved in causing cancer. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes...
ic.
Thorium-233
233Th is an isotope of thoriumThorium
Thorium is a natural radioactive chemical element with the symbol Th and atomic number 90. It was discovered in 1828 and named after Thor, the Norse god of thunder....
that decays into protactinium-233 through beta decay. It has a half-life of 21.83 minutes.
Thorium-234
234Th is an isotopeIsotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
of thorium
Thorium
Thorium is a natural radioactive chemical element with the symbol Th and atomic number 90. It was discovered in 1828 and named after Thor, the Norse god of thunder....
whose nuclei
Atomic nucleus
The nucleus is the very dense region consisting of protons and neutrons at the center of an atom. It was discovered in 1911, as a result of Ernest Rutherford's interpretation of the famous 1909 Rutherford experiment performed by Hans Geiger and Ernest Marsden, under the direction of Rutherford. The...
contain 144 neutron
Neutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
s. Th-234 has a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of about 24.1 days, and when it decays, it emits a beta particle
Beta particle
Beta particles are high-energy, high-speed electrons or positrons emitted by certain types of radioactive nuclei such as potassium-40. The beta particles emitted are a form of ionizing radiation also known as beta rays. The production of beta particles is termed beta decay...
, and in so doing, it transmutes into protactinium
Protactinium
Protactinium is a chemical element with the symbol Pa and atomic number 91. It is a dense, silvery-gray metal which readily reacts with oxygen, water vapor and inorganic acids. It forms various chemical compounds where protactinium is usually present in the oxidation state +5, but can also assume...
-234. Th-234 has a mass of about 234.0436 atomic mass unit
Atomic mass unit
The unified atomic mass unit or dalton is a unit that is used for indicating mass on an atomic or molecular scale. It is defined as one twelfth of the rest mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state, and has a value of...
s (amu
AMU
As an abbreviation, AMU may refer to:* Adam Mickiewicz University, Poznań, Poland* African Mathematical Union* Aligarh Muslim University, Aligarh, India* American Military University, Charles Town, West Virginia* Arab Maghreb Union...
), and it has a decay energy of about 270 KeV (kiloelectron-volts). Uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
-238 usually decays into this isotope of thorium. (It can undergo spontaneous fission
Spontaneous fission
Spontaneous fission is a form of radioactive decay characteristic of very heavy isotopes. Because the nuclear binding energy reaches a maximum at a nuclear mass greater than about 60 atomic mass units , spontaneous breakdown into smaller nuclei and single particles becomes possible at heavier masses...
.)
Table
| nuclide symbol |
historic name |
Z(p Proton The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number.... ) |
N(n Neutron The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of... ) |
isotopic mass (u) |
half-lifeBold for nuclides with half-lives longer than the age of the universe (nearly stable) | decay mode(s)Abbreviations: CD: Cluster decay Cluster decay Cluster decay is a type of nuclear decay in which a parent atomic nucleus with A nucleons and Z protons emits a cluster of Ne neutrons and Ze protons heavier than an alpha particle but lighter than a typical binary fission fragment Cluster decay (also named heavy particle radioactivity or heavy... EC: Electron capture Electron capture Electron capture is a process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino... IT: Isomeric transition Isomeric transition An isomeric transition is a radioactive decay process that involves emission of a gamma ray from an atom where the nucleus is in an excited metastable state, referred to in its excited state, as a nuclear isomer.... SF: Spontaneous fission Spontaneous fission Spontaneous fission is a form of radioactive decay characteristic of very heavy isotopes. Because the nuclear binding energy reaches a maximum at a nuclear mass greater than about 60 atomic mass units , spontaneous breakdown into smaller nuclei and single particles becomes possible at heavier masses... |
daughter isotopes(s)Bold for stable isotopes |
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] |
α Alpha decay Alpha decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle and thereby transforms into an atom with a mass number 4 less and atomic number 2 less... |
206Ra | 0+ | |||
| β+ Beta decay In nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a... (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 Electron capture Electron capture is a process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino... (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+ | TraceIntermediate decay product Decay product In nuclear physics, a decay product is the remaining nuclide left over from radioactive decay. Radioactive decay often involves a sequence of steps... of 235U Uranium-235 - References :* .* DOE Fundamentals handbook: Nuclear Physics and Reactor theory , .* A piece of U-235 the size of a grain of rice can produce energy equal to that contained in three tons of coal or fourteen barrels of oil. -External links:* * * one of the earliest articles on U-235 for the... |
|
| 228Th | Radiothorium | 90 | 138 | 228.0287411(24) | 1.9116(16) a | α | 224Ra | 0+ | TraceIntermediate decay product of 232Th | |
| CD Cluster decay Cluster decay is a type of nuclear decay in which a parent atomic nucleus with A nucleons and Z protons emits a cluster of Ne neutrons and Ze protons heavier than an alpha particle but lighter than a typical binary fission fragment Cluster decay (also named heavy particle radioactivity or heavy... (1.3×10−11%) |
208Pb 20O |
|||||||||
| 229Th | 90 | 139 | 229.031762(3) | 7.34(16)×103 a | α | 225Ra | 5/2+ | |||
| 229mTh | 0.0076(5) keV | 70(50) h | IT Isomeric transition An isomeric transition is a radioactive decay process that involves emission of a gamma ray from an atom where the nucleus is in an excited metastable state, referred to in its excited state, as a nuclear isomer.... |
229Th | 3/2+ | |||||
| 230ThUsed in Uranium-thorium dating Uranium-thorium dating Uranium-thorium dating, also called thorium-230 dating, uranium-series disequilibrium dating or uranium-series dating, is a radiometric dating technique commonly used to determine the age of calcium carbonate materials such as speleothem or coral... |
Ionium | 90 | 140 | 230.0331338(19) | 7.538(30)×104 a | α | 226Ra | 0+ | TraceIntermediate decay product of 238U Uranium-238 Uranium-238 is the most common isotope of uranium found in nature. It is not fissile, but is a fertile material: it can capture a slow neutron and after two beta decays become fissile plutonium-239... |
|
| CD (5.6×10−11%) | 206Hg 24Ne |
|||||||||
| SF Spontaneous fission Spontaneous fission is a form of radioactive decay characteristic of very heavy isotopes. Because the nuclear binding energy reaches a maximum at a nuclear mass greater than about 60 atomic mass units , spontaneous breakdown into smaller nuclei and single particles becomes possible at heavier masses... (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 | |||||||||
| 232ThPrimordial Primordial nuclide In geochemistry and geonuclear physics, primordial nuclides or primordial isotopes are nuclides found on the earth that have existed in their current form since before Earth was formed. Only 288 such nuclides are known... radionuclide Radionuclide A radionuclide is an atom with an unstable nucleus, which is a nucleus characterized by excess energy available to be imparted either to a newly created radiation particle within the nucleus or to an atomic electron. The radionuclide, in this process, undergoes radioactive decay, and emits gamma... |
Thorium | 90 | 142 | 232.0380553(21) | 1.405(6)×1010 a | α | 228Ra | 0+ | 1.0000 | |
| 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+ | |||