What are the naturally occurring isotopes of thorium?

Thorium (Th) has seven naturally occurring isotopes, but none of them are stable. The most abundant and relatively stable isotope is Thorium-232 (²³²Th).

What is the half-life of Thorium-232 (²³²Th) and how does it compare to the age of the Earth and universe?

Thorium-232 (²³²Th) has a half-life of 1.40 x 10¹⁰ years. This duration is considerably longer than the age of the Earth and slightly longer than the generally accepted age of the universe.

Why was thorium initially considered mononuclidic?

Thorium was initially considered mononuclidic because Thorium-232 (²³²Th) makes up nearly all natural thorium, with other isotopes present only in trace amounts as decay products.

How did IUPAC reclassify thorium in 2013, and why?

In 2013, IUPAC reclassified thorium as binuclidic due to the discovery of large quantities of Thorium-230 (²³⁰Th) in deep seawater, indicating a more complex terrestrial isotopic composition than previously recognized.

How many radioisotopes of thorium have been characterized, and which are the most stable?

Thirty-one radioisotopes of thorium have been characterized. The most stable among these are Thorium-232 (²³²Th), Thorium-230 (²³⁰Th) with a half-life of 75,400 years, Thorium-229 (²²⁹Th) with a half-life of 7,916 years, and Thorium-228 (²²⁸Th) with a half-life of 1.91 years.

What is the half-life range for the majority of thorium's radioactive isotopes?

The majority of thorium's radioactive isotopes have half-lives shorter than thirty days, with most having half-lives of less than ten minutes.

What is unique about the nuclear isomer of Thorium-229 (²²⁹Th)?

Thorium-229 has a nuclear isomer, known as ²²⁹mTh, which possesses a remarkably low excitation energy, recently measured to be approximately 8.355 eV. This low energy transition is being explored for applications like highly accurate nuclear clocks.

What is the mass number range for known thorium isotopes?

The known isotopes of thorium span a mass number range from 207 to 238.

What are the primary decay modes listed for thorium isotopes in the main table?

The primary decay modes listed for thorium isotopes include alpha decay (α) and beta-minus decay (β⁻). Some isotopes also undergo isomeric transition (IT) or cluster decay (CD).

Which thorium isotope is primarily responsible for thorium's natural abundance?

Thorium-232 (²³²Th) is the primordial nuclide of thorium and accounts for virtually all of its natural abundance, with other isotopes occurring only in trace amounts as decay products.

What is the historical name for Thorium-230 (²³⁰Th)?

The isotope Thorium-230 (²³⁰Th) was historically known as Ionium (Io).

What is Thorium-231 (²³¹Th) a decay product of, and what does it decay into?

Thorium-231 (²³¹Th) is a decay product of Uranium-235 (²³⁵U). When it decays via beta-minus emission, it transforms into Protactinium-231 (²³¹Pa).

How is Thorium-232 (²³²Th) utilized in the context of nuclear energy?

Thorium-232 (²³²Th) is a fertile material that can absorb a neutron and transmute into Uranium-233 (²³³U), which is a fissile nuclide. This process forms the basis of the thorium fuel cycle.

What historical medical application involved Thorium-232 (²³²Th)?

Thorium-232 (²³²Th), in the form of Thorotrast (a thorium dioxide suspension), was used as a contrast medium in early X-ray diagnostics. However, it is now classified as carcinogenic.

What is Thorium-233 (²³³Th) a decay product of, and what series does it join?

Thorium-233 (²³³Th) decays via beta-minus emission into Protactinium-233 (²³³Pa), which then decays into Uranium-233 (²³³U), thus joining the neptunium series decay chain.

What is Thorium-234 (²³⁴Th) a decay product of, and what does it decay into?

Thorium-234 (²³⁴Th) is produced from the decay of Uranium-238 (²³⁸U). It decays via beta-minus emission into Protactinium-234 (²³⁴Pa).

What is the significance of the low excitation energy of the Thorium-229m isomer (²²⁹mTh)?

The remarkably low excitation energy of ²²⁹mTh, around 8.355 eV, is significant because it is low enough to potentially be controlled by lasers, opening possibilities for applications such as highly accurate nuclear clocks and qubits for quantum computing.

How does the electronic environment affect the lifetime of the ²²⁹mTh nuclear isomer?

The lifetime of the ²²⁹mTh isomer is significantly influenced by its electronic environment. In neutral thorium atoms, it decays rapidly via internal conversion within microseconds. However, in Th⁺ ions, where internal conversion is inhibited due to insufficient energy to remove a second electron, radiative decay occurs with a much longer half-life.

What are the potential applications of the ²²⁹mTh nuclear isomer?

The ²²⁹mTh nuclear isomer's low excitation energy makes it a candidate for developing nuclear clocks with extremely high accuracy and for use as a qubit in quantum computing, due to the possibility of laser excitation.

What historical challenges existed in precisely measuring the energy of the ²²⁹mTh isomer?

For a long time, precise measurements of the ²²⁹mTh isomer's energy were challenging. Early methods like gamma-ray spectroscopy provided estimates, but the low energy made direct observation difficult, leading to various theoretical and experimental efforts to constrain its value.

What recent advancements have been made in measuring the ²²⁹mTh isomer's energy?

Recent advancements, particularly in 2024, have involved laser spectroscopy on Th⁴⁺ cations within ionic crystals (like CaF₂ and LiSrAlF₆). These experiments have yielded highly precise measurements of the transition energy, approaching part-per-million accuracy, and have also provided more accurate lifetime measurements.

What is Thorium-228 (²²⁸Th) used for in medical applications?

Thorium-228 (²²⁸Th), along with its decay product Radium-224 (²²⁴Ra), is used for alpha particle radiation therapy in cancer treatment.

What medical isotopes are produced from the decay of Thorium-229 (²²⁹Th)?

Thorium-229 (²²⁹Th) is primarily used for the production of the medical isotopes Actinium-225 (²²⁵Ac) and Bismuth-213 (²¹³Bi).

What is Thorium-230 (²³⁰Th) used for in scientific dating methods?

Thorium-230 (²³⁰Th) is utilized in dating methods such as uranium-thorium dating, which is used to date corals, and also in ionium-thorium dating. It also helps in determining ocean current flux.

What is the decay energy of Thorium-231 (²³¹Th) when it emits a beta ray?

When Thorium-231 (²³¹Th) decays by emitting a beta ray, it does so with a decay energy of approximately 0.39 MeV.

What is the decay chain of Thorium-232 (²³²Th) called, and what is its final stable product?

The decay chain of Thorium-232 (²³²Th) is known as the thorium series. This series eventually terminates with the stable isotope Lead-208 (²⁰⁸Pb).

What are the longest-lived isotopes within the Thorium-232 (²³²Th) decay chain, besides ²³²Th itself?

Besides Thorium-232 (²³²Th), the longest-lived isotopes in its decay chain are Radium-228 (²²⁸Ra) with a half-life of 5.75 years and Thorium-228 (²²⁸Th) with a half-life of 1.91 years. All other isotopes in the chain have half-lives totaling less than a week.

What is Thorium-234 (²³⁴Th) known for in relation to Uranium-238 (²³⁸U) decay?

Thorium-234 (²³⁴Th) is a direct decay product of Uranium-238 (²³⁸U). While ²³⁸U typically decays via alpha emission, it can very rarely undergo spontaneous fission or double beta decay, but its primary decay path leads to ²³⁴Th.

What were Kodak Aero-Ektar lenses, and why did they contain thorium?

Kodak Aero-Ektar lenses, used during World War II, incorporated thorium in some of their glass elements. This was done because thorium-containing glasses possess a high refractive index combined with low dispersion, properties highly desirable for lens optics.

Were Kodak Aero-Ektar lenses considered safe for use despite containing thorium?

Yes, the Kodak Aero-Ektar lenses were considered safe enough for aerial reconnaissance use because the radiation level was not high enough to fog photographic film over short exposure periods. However, it is prudent to store them away from populated areas to minimize radiation exposure due to the inverse square law.

What is the significance of the '4n' decay chain classification mentioned in the table?

The '4n' classification in the 'Actinides vs. fission products' table refers to decay chains where the mass number (A) is a multiple of 4. Thorium-232 (²³²Th) belongs to the 4n decay chain, which ultimately leads to stable Lead-208 (²⁰⁸Pb).

What is the historical name 'Radiothorium' associated with?

The historical name Radiothorium was given to Thorium-228 (²²⁸Th) due to its presence in the disintegration chain of Thorium-232 (²³²Th).

What is the half-life of Thorium-229 (²²⁹Th) and its primary decay product?

Thorium-229 (²²⁹Th) has a half-life of 7,916 years and decays primarily through alpha emission, producing Radium-225 (²²⁵Ra).

What is the excitation energy of the ²²⁹mTh isomer, and what is its significance?

The nuclear isomer ²²⁹mTh has an excitation energy of approximately 8.355 eV. This extremely low energy is significant because it is the lowest known excitation energy for a nuclear state, making it a potential candidate for a nuclear clock.

What was the initial estimate for the excitation energy of ²²⁹mTh, and how has it evolved?

Initial estimates for the ²²⁹mTh isomer's excitation energy were below 100 eV, later refined to below 10 eV. More recent measurements have narrowed this down significantly, with values around 8.355 eV being reported, though precise determination has been a long-standing challenge.

What are the implications of the ²²⁹mTh isomer's excitation energy being above the first ionization energy of thorium?

Since the excitation energy of ²²⁹mTh (approx. 8.355 eV) is higher than thorium's first ionization energy (approx. 6.08 eV), neutral ²²⁹mTh atoms are expected to decay radiatively with a very low probability, as the energy is sufficient to ionize the atom.

Why are photons emitted by the ²²⁹mTh isomer's decay not visible in air?

The photons emitted by the ²²⁹mTh isomer's decay have a frequency corresponding to the vacuum ultraviolet (VUV) range. This is because the excitation energy (approx. 8.355 eV) is above the VUV cutoff, meaning these photons cannot travel through air.

What was the conclusion of Kroger and Reich's 1976 study regarding ²²⁹Th?

In 1976, Kroger and Reich concluded that some previously identified states of ²²⁹Th likely originated from a nuclear isomer, ²²⁹mTh, with a remarkably low excitation energy, based on difficulties in classifying known nuclear states according to theoretical models.

What is the half-life of Thorium-231 (²³¹Th), and what is its decay energy?

Thorium-231 (²³¹Th) has a half-life of 25.52 hours and decays with an energy of approximately 0.39 MeV.

What is the half-life of Thorium-233 (²³³Th), and what decay series does it belong to?

Thorium-233 (²³³Th) has a half-life of 21.83 minutes. It decays via beta emission, leading to Protactinium-233 (²³³Pa), and subsequently joins the neptunium series decay chain.

What is the half-life of Thorium-234 (²³⁴Th), and what does it decay into?

Thorium-234 (²³⁴Th) has a half-life of 24.11 days. It decays by emitting a beta particle, transforming into Protactinium-234 (²³⁴Pa).

What is the half-life of Thorium-228 (²²⁸Th), and what are its decay modes?

Thorium-228 (²²⁸Th) has a half-life of 1.9125 years. It primarily decays via alpha decay to Radium-224 (²²⁴Ra), but can occasionally undergo cluster decay by emitting an Oxygen-18 nucleus and producing stable Lead-208 (²⁰⁸Pb).

What is the half-life of Thorium-227 (²²⁷Th), and what is its historical name?

Thorium-227 (²²⁷Th) has a half-life of 18.693 days and was historically known as Radioactinium.

What is the half-life of Thorium-229 (²²⁹Th), and what is its primary decay mode?

Thorium-229 (²²⁹Th) has a half-life of 7,916 years and decays via alpha emission to Radium-225 (²²⁵Ra).

What is the half-life of Thorium-230 (²³⁰Th), and what is its significance in dating?

Thorium-230 (²³⁰Th) has a half-life of 75,400 years and is used in uranium-thorium dating methods, particularly for materials like corals, and also for studying ocean current dynamics.

What is the half-life of Thorium-232 (²³²Th), and what is its classification regarding natural occurrence?

Thorium-232 (²³²Th) has a very long half-life of 1.40 x 10¹⁰ years, making it the only primordial nuclide of thorium and accounting for almost all of its natural presence.

What are the half-lives of the isotopes Thorium-216 (²¹⁶Th) and Thorium-217 (²¹⁷Th)?

Thorium-216 (²¹⁶Th) has a half-life of 26.28 milliseconds, while Thorium-217 (²¹⁷Th) has a half-life of 248 microseconds.

What is the half-life of Thorium-219 (²¹⁹Th)?

Thorium-219 (²¹⁹Th) has a half-life of 1.023 microseconds.

What is the half-life of Thorium-221 (²²¹Th)?

Thorium-221 (²²¹Th) has a half-life of 1.75 milliseconds.

What is the half-life of Thorium-223 (²²³Th)?

Thorium-223 (²²³Th) has a half-life of 0.60 seconds.

What is the half-life of Thorium-224 (²²⁴Th)?

Thorium-224 (²²⁴Th) has a half-life of 1.04 seconds.

Isotopes Of Thorium Wiki: Thorium's Atomic Tapestry: An Isotopic Exploration

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Introduction to Thorium Isotopes

Natural Occurrence

Thorium (₉₀Th) is an element characterized by its naturally occurring isotopes. While it possesses seven naturally occurring isotopes, none are stable. A key isotope, ²³²Th, stands out with a remarkably long half-life of 1.40×10¹⁰ years, significantly exceeding the age of the Earth and even the estimated age of the universe. This extended stability means ²³²Th constitutes nearly all natural thorium, historically leading to its classification as a mononuclidic element.

Reclassification and Abundance

However, in 2013, the International Union of Pure and Applied Chemistry (IUPAC) reclassified thorium as binuclidic. This change was prompted by the discovery of significant quantities of ²³⁰Th in deep seawater. Thorium exhibits a characteristic terrestrial isotopic composition, allowing for the definition of a standard atomic weight.

Radioisotopes and Stability

Beyond the naturally abundant isotopes, thirty-one radioisotopes of thorium have been identified and characterized. Among these, ²³²Th, ²³⁰Th (with a half-life of 75,400 years), ²²⁹Th (7,916 years), and ²²⁸Th (1.91 years) are the most stable. The remaining radioactive isotopes possess half-lives of less than thirty days, with many decaying in mere minutes.

Comprehensive Isotope Data

Isotope Inventory

The following table provides a detailed overview of Thorium's isotopes, including their mass number, historical names, atomic and neutron counts, isotopic mass, half-life, decay modes, daughter products, nuclear spin, parity, and natural abundance where applicable.

Isotopes of Thorium (₉₀Th)

Main isotopes^[1]			Decay
Isotope	abundance	half-life (t_1/2)	mode	product
²²⁷Th	trace	18.693 d	α	²²³Ra
²²⁸Th	trace	1.9125 y	α	²²⁴Ra
²²⁹Th	trace	7916 y	α	²²⁵Ra
²³⁰Th	0.02%	75400 y	α	²²⁶Ra
²³¹Th	trace	25.52 h	β^-	²³¹Pa
²³²Th	100.0%	1.40×10¹⁰ y	α	²²⁸Ra
²³³Th	trace	21.83 min	β^-	²³³Pa
²³⁴Th	trace	24.11 d	β^-	²³⁴Pa

Standard atomic weight A_r°(Th)

232.0377±0.0004^[2]
232.04±0.01 (abridged)^[3]

Nuclide ^{[n 1]}	Historic name	Z	N	Isotopic mass (Da)^[11] ^{[n 2]}^{[n 3]}	Half-life^[1] ^{[n 4]}	Decay mode^[1] ^{[n 5]}	Daughter isotope ^{[n 6]}	Spin and parity^[1] ^{[n 7]}^{[n 8]}	Natural abundance
Nuclide ^{[n 1]}	Historic name	Excitation energy			Half-life^[1] ^{[n 4]}	Decay mode^[1] ^{[n 5]}	Daughter isotope ^{[n 6]}	Spin and parity^[1] ^{[n 7]}^{[n 8]}	Normal proportion^[1]	Range of variation
²⁰⁷Th^[10]		90	117		9.7+46.6 −4.4 ms	α	²⁰³Ra
²⁰⁸Th		90	118	208.017915(34)	2.4(12) ms	α	²⁰⁴Ra	0+
²⁰⁹Th		90	119	209.017998(27)	3.1(12) ms	α	²⁰⁵Ra	13/2+
²¹⁰Th		90	120	210.015094(20)	16.0(36) ms	α	²⁰⁶Ra	0+
²¹¹Th		90	121	211.014897(92)	48(20) ms	α	²⁰⁷Ra	5/2−#
²¹²Th		90	122	212.013002(11)	31.7(13) ms	α	²⁰⁸Ra	0+
²¹³Th		90	123	213.0130115(99)	144(21) ms	α	²⁰⁹Ra	5/2−
^213mTh		1180.0(14) keV			1.4(4) μs	IT	²¹³Th	(13/2)+
²¹⁴Th		90	124	214.011481(11)	87(10) ms	α	²¹⁰Ra	0+
^214mTh		2181.0(27) keV			1.24(12) μs	IT	²¹⁴Th	8+#
²¹⁵Th		90	125	215.0117246(68)	1.35(14) s	α	²¹¹Ra	(1/2−)
^215mTh		1471(50)# keV			770(60) ns	IT	²¹⁵Th	9/2+#
²¹⁶Th		90	126	216.011056(12)	26.28(16) ms	α	²¹²Ra	0+
^216m1Th		2041(8) keV			135.4(29) μs	IT (97.2%)	²¹⁶Th	8+
^216m1Th		2041(8) keV			135.4(29) μs	α (2.8%)	²¹²Ra	8+
^216m2Th		2648(8) keV			580(26) ns	IT	²¹⁶Th	(11−)
^216m3Th		3682(8) keV			740(70) ns	IT	²¹⁶Th	(14+)
²¹⁷Th		90	127	217.013103(11)	248(4) μs	α	²¹³Ra	9/2+#
^217m1Th		673.3(1) keV			141(50) ns	IT	²¹⁷Th	(15/2−)
^217m2Th		2307(32) keV			71(14) μs	IT	²¹⁷Th	(25/2+)
²¹⁸Th		90	128	218.013276(11)	122(5) ns	α	²¹⁴Ra	0+
²¹⁹Th		90	129	219.015526(61)	1.023(18) μs	α	²¹⁵Ra	9/2+#
²²⁰Th		90	130	220.015770(15)	10.2(3) μs	α	²¹⁶Ra	0+
²²¹Th		90	131	221.0181858(86)	1.75(2) ms	α	²¹⁷Ra	7/2+#
²²²Th		90	132	222.018468(11)	2.24(3) ms	α	²¹⁸Ra	0+
²²³Th		90	133	223.0208111(85)	0.60(2) s	α	²¹⁹Ra	(5/2)+
²²⁴Th		90	134	224.021466(10)	1.04(2) s	α^{[n 9]}	²²⁰Ra	0+
²²⁵Th		90	135	225.0239510(55)	8.75(4) min	α (~90%)	²²¹Ra	3/2+
²²⁵Th		90	135	225.0239510(55)	8.75(4) min	EC (~10%)	²²⁵Ac	3/2+
²²⁶Th		90	136	226.0249037(48)	30.70(3) min	α	²²²Ra	0+
²²⁶Th		90	136	226.0249037(48)	30.70(3) min	CD (<3.2×10⁻¹²%)	²⁰⁸Pb ¹⁸O	0+
²²⁷Th	Radioactinium	90	137	227.0277025(22)	18.693(4) d	α	²²³Ra	(1/2+)	Trace^{[n 10]}
²²⁸Th	Radiothorium	90	138	228.0287397(19)	1.9125(7) y	α	²²⁴Ra	0+	Trace^{[n 11]}
²²⁸Th	Radiothorium	90	138	228.0287397(19)	1.9125(7) y	CD (1.13×10⁻¹¹%)	²⁰⁸Pb ²⁰O	0+	Trace^{[n 11]}
²²⁹Th		90	139	229.0317614(26)	7916(17) y	α	²²⁵Ra	5/2+	Trace^{[n 12]}
^229mTh		8.355733554021(8) eV^[6]			7(1) μs^[12]	IT^{[n 13]}	²²⁹Th⁺	3/2+
^229mTh⁺		8.355733554021(8) eV^[6]			29(1) min^[13]	γ^{[n 13]}	²²⁹Th⁺	3/2+
²³⁰Th^{[n 14]}	Ionium	90	140	230.0331323(13)	7.54(3)×10⁴ y	α	²²⁶Ra	0+	0.0002(2)^{[n 15]}
						CD (5.8×10⁻¹¹%)	²⁰⁶Hg ²⁴Ne
						SF (<4×10⁻¹²%)	(various)
²³¹Th	Uranium Y	90	141	231.0363028(13)	25.52(1) h	β⁻	²³¹Pa	5/2+	Trace^{[n 10]}
²³²Th^{[n 16]}	Thorium	90	142	232.0380536(15)	1.40(1)×10¹⁰ y	α^{[n 17]}	²²⁸Ra	0+	0.9998(2)
						SF (1.1 × 10⁻⁹%)	(various)
						CD (<2.78×10⁻¹⁰%)	^208,206Hg ^24,26Ne
²³³Th		90	143	233.0415801(15)	21.83(4) min	β⁻	²³³Pa	1/2+	Trace^{[n 18]}
²³⁴Th	Uranium X₁	90	144	234.0435998(28)	24.107(24) d	β⁻	^234mPa^[14]	0+	Trace^{[n 15]}
²³⁵Th		90	145	235.047255(14)	7.2(1) min	β⁻	²³⁵Pa	1/2+#
²³⁶Th		90	146	236.049657(15)	37.3(15) min	β⁻	²³⁶Pa	0+
²³⁷Th		90	147	237.053629(17)	4.8(5) min	β⁻	²³⁷Pa	5/2+#
²³⁸Th		90	148	238.05639(30)#	9.4(20) min	β⁻	²³⁸Pa	0+
This table header & footer: view

^ ^mTh – Excited nuclear isomer.
^ ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
^ # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
^ Bold half-life – nearly stable, half-life longer than age of universe.
^ Modes of decay:
^ Bold symbol as daughter – Daughter product is stable.
^ ( ) spin value – Indicates spin with weak assignment arguments.
^ # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
^ Theorized to also undergo β⁺β⁺ decay to ²²⁴Ra
^ ^a ^b Intermediate decay product of ²³⁵U
^ Intermediate decay product of ²³²Th
^ Intermediate decay product of ²³⁷Np
^ ^a ^b Neutral ^229mTh decays rapidly by internal conversion, ejecting an electron. There is not enough energy to eject a second electron, so ^229mTh⁺ ions live much longer, decaying by gamma emission. See § Thorium-229m.
^ Used in uranium–thorium dating
^ ^a ^b Intermediate decay product of ²³⁸U

Notable Thorium Isotopes

Thorium-228 (Radiothorium)

²²⁸Th is an isotope of thorium with 138 neutrons. It is part of the decay chain of ²³²Th, historically earning it the name Radiothorium. With a half-life of 1.9125 years, it primarily decays via alpha emission to ²²⁴Ra. Unusually, it can also undergo cluster decay, emitting a ²⁰O nucleus and producing stable ²⁰⁸Pb. ²²⁸Th is a daughter isotope of ²³²U and contributes significantly to its radiological hazard. It finds application in alpha particle radiation therapy, often in conjunction with its decay product ²²⁴Ra.

Thorium-229

²²⁹Th is a radioactive isotope of thorium that decays via alpha emission with a half-life of 7916 years. It is generated from the decay of uranium-233 and is crucial for producing medical isotopes like actinium-225 and bismuth-213. A unique characteristic of ²²⁹Th is its nuclear isomer, ^229mTh, which possesses an exceptionally low excitation energy (around 8.3 eV). This property has spurred research into developing highly accurate nuclear clocks and exploring quantum computing applications, though precise measurements of its transition energy have been a long-standing challenge.

Thorium-230 (Ionium)

²³⁰Th is a radioactive isotope of thorium utilized in dating methods such as uranium-thorium dating for corals and determining ocean current flux. Historically known as Ionium (Io), this isotope is produced in the decay chain of uranium-238. The name "Ionium" persists in the ionium-thorium dating technique. Its presence in deep seawater led to the reclassification of thorium as binuclidic.

Thorium-232

²³²Th is the sole primordial nuclide of thorium, making up virtually all natural thorium. Its alpha decay half-life of 1.40×10¹⁰ years is longer than the age of the Earth. It initiates the thorium series decay chain, ultimately leading to stable lead-208. The longest-lived intermediates in this chain are radium-228 (5.75 years) and thorium-228 (1.91 years). ²³²Th is a fertile material, capable of absorbing neutrons to transmute into the fissile nuclide uranium-233, forming the basis of the thorium fuel cycle. Historically used in Thorotrast, a thorium dioxide suspension, as an X-ray contrast medium, it is now classified as carcinogenic.

Applications and Significance

Nuclear Energy

Thorium, particularly the isotope ²³²Th, is a key component in the proposed thorium fuel cycle. It acts as a fertile material, capable of absorbing neutrons to produce fissile uranium-233. This cycle offers potential advantages in nuclear power generation, including reduced long-lived waste and improved safety characteristics.

Industrial and Scientific Uses

Thorium compounds have found use in various industrial applications. Thorium dioxide (ThO₂) was historically employed in gas mantles for lamps, providing intense light upon incandescence. It also served as a cathode material in vacuum tubes due to its thermal stability and low work function for electron emission. Certain specialized lenses, like Kodak's Aero-Ektar, utilized thorium-containing glass for its high refractive index and low dispersion properties, though these lenses exhibit mild radioactivity.

Medical and Research Applications

Specific thorium isotopes, such as ²²⁸Th and its decay products, are investigated and used in targeted alpha therapy for cancer treatment. Furthermore, the unique properties of the ²²⁹Th nuclear isomer are being explored for the development of highly precise nuclear clocks and potentially for quantum computing applications, representing cutting-edge research in nuclear physics and metrology.

Historical Context

Early Discoveries and Naming

The study of thorium's isotopes has a rich history. The isotope ²³⁰Th was initially named "Ionium" before the concept of isotopes was fully understood. Early research into radioactive decay chains, particularly those originating from uranium, revealed the existence and properties of various thorium isotopes. The long half-life of ²³²Th established it as a primordial nuclide, forming the backbone of the thorium decay series.

Isomeric State Research

Significant scientific effort has been dedicated to understanding the low-lying nuclear isomer of ²²⁹Th (^229mTh). The precise measurement of its excitation energy and lifetime has been a complex endeavor, involving advanced spectroscopic techniques. Recent breakthroughs in laser spectroscopy have provided highly accurate values for this energy, paving the way for practical applications like nuclear clocks.

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References

mTh – Excited nuclear isomer.

( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.

# – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).

Bold half-life – nearly stable, half-life longer than age of universe.

# – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).

Intermediate decay product of 235U

Intermediate decay product of 237Np

Used in uraniumâthorium dating

Primordial radionuclide

Specifically from thermal neutron fission of uranium-235, e.g. in a typical nuclear reactor.

This is the heaviest nuclide with a half-life of at least four years before the "sea of instability".

A full list of references for this article are available at the Isotopes of thorium Wikipedia page

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Important Disclaimer

Scientific Data and Safety Notice

This content has been generated by an AI model based on publicly available scientific data. While efforts have been made to ensure accuracy and adherence to the source material, it is intended for informational and educational purposes only. Thorium and its isotopes are radioactive materials and may pose health risks. Handling or exposure should only be done under strict safety protocols and expert supervision.

This is not professional advice. The information provided does not substitute for expert consultation in nuclear physics, materials science, or radiation safety. Always consult official documentation and qualified professionals for any practical applications or safety concerns related to radioactive materials.

The creators of this page are not liable for any errors, omissions, or consequences arising from the use of this information.

Thorium's Atomic Tapestry

💡 Dive in with Flashcard Learning! 💡

Introduction to Thorium Isotopes ⚛️

🌟 Natural Occurrence

🌊 Reclassification and Abundance

🔬 Radioisotopes and Stability

Comprehensive Isotope Data 📊

🗂️ Isotope Inventory

Notable Thorium Isotopes ⭐

☢️ Thorium-228 (Radiothorium)

⏳ Thorium-229

🗓️ Thorium-230 (Ionium)

🌍 Thorium-232

Applications and Significance 💡

⚡ Nuclear Energy

💡 Industrial and Scientific Uses

🔬 Medical and Research Applications

Historical Context 📜

🕰️ Early Discoveries and Naming

🔬 Isomeric State Research

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Important Disclaimer ⚠️

📜 Scientific Data and Safety Notice

Dive in with Flashcard Learning!

Introduction to Thorium Isotopes

Natural Occurrence

Reclassification and Abundance

Radioisotopes and Stability

Comprehensive Isotope Data

Isotope Inventory

Notable Thorium Isotopes

Thorium-228 (Radiothorium)

Thorium-229

Thorium-230 (Ionium)

Thorium-232

Applications and Significance

Nuclear Energy

Industrial and Scientific Uses

Medical and Research Applications

Historical Context

Early Discoveries and Naming

Isomeric State Research

Teacher's Corner

True or False?

Test Your Knowledge!

Gamer's Corner

Discover other topics to study!

References

Feedback & Support

Important Disclaimer

Scientific Data and Safety Notice