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Thorium possesses precisely one stable, naturally occurring isotope.
Answer: False
Explanation: While Thorium-232 is the most abundant and longest-lived isotope, no naturally occurring isotopes of thorium are truly stable. Other isotopes exist transiently as decay products.
Thorium was initially classified as mononuclidic due to the prevailing understanding that Thorium-232 was its sole known isotope.
Answer: False
Explanation: The initial classification of thorium as mononuclidic stemmed from Thorium-232 (²³²Th) constituting nearly all natural thorium, with other isotopes being present only in trace amounts as decay products.
Thirty-one radioisotopes of thorium have been characterized; Thorium-232 is recognized as the most stable among them.
Answer: True
Explanation: A total of thirty-one radioisotopes of thorium have been identified. Thorium-232 (²³²Th) is distinguished as the most stable isotope within this group.
The known isotopes of thorium span a mass number range extending from 230 to 238.
Answer: False
Explanation: The known isotopes of thorium encompass a broader mass number range, from 207 to 238, not exclusively 230 to 238.
Alpha decay represents the sole observed decay mode for all known thorium isotopes.
Answer: False
Explanation: Thorium isotopes exhibit multiple decay modes, including alpha decay (α), beta-minus decay (β⁻), and isomeric transition (IT), among others.
Thorium-232 serves as the principal isotope contributing to thorium's natural abundance.
Answer: True
Explanation: Thorium-232 (²³²Th) is the primordial nuclide of thorium and accounts for virtually all of its natural presence on Earth.
Identify the most abundant and relatively stable naturally occurring isotope of thorium.
Answer: Thorium-232 (²³²Th)
Explanation: Thorium-232 (²³²Th) is the primordial nuclide of thorium, making it the most abundant and relatively stable isotope found naturally.
What was the rationale behind initially classifying thorium as a mononuclidic element?
Answer: Thorium-232 constituted almost all natural thorium, with other isotopes being extremely rare.
Explanation: Thorium was initially considered mononuclidic because Thorium-232 (²³²Th) comprises nearly all of its natural abundance, with other isotopes present only in trace quantities as decay products.
Which of the following decay modes is not identified as a primary mode for thorium isotopes within the provided data?
Answer: Electron capture (EC)
Explanation: While alpha decay (α), beta-minus decay (β⁻), and isomeric transition (IT) are mentioned or implied for various thorium isotopes, electron capture (EC) is not explicitly listed as a primary decay mode in the source material.
Thorium-232 (²³²Th) exhibits a half-life considerably shorter than the age of the Earth.
Answer: False
Explanation: Thorium-232 (²³²Th) possesses a half-life of approximately 1.40 x 10¹⁰ years, which is substantially longer than the age of the Earth.
The majority of thorium's radioactive isotopes possess half-lives exceeding one year.
Answer: False
Explanation: Contrary to the assertion, the majority of thorium's radioactive isotopes exhibit half-lives significantly shorter than one year, with most decaying in minutes or less.
Thorium-231 undergoes decay into Protactinium-231 via alpha emission.
Answer: False
Explanation: Thorium-231 (²³¹Th) decays into Protactinium-231 (²³¹Pa) primarily through beta-minus emission, not alpha emission.
Thorium-233 decays into Uranium-233, subsequently joining the thorium series.
Answer: False
Explanation: Thorium-233 (²³³Th) decays to Protactinium-233 (²³³Pa), which then decays to Uranium-233 (²³³U). This sequence leads into the neptunium series, not the thorium series.
Thorium-234 is a direct decay product of Uranium-238 and subsequently decays into Protactinium-234.
Answer: True
Explanation: Thorium-234 (²³⁴Th) is indeed a decay product originating from Uranium-238 (²³⁸U) and decays via beta-minus emission to Protactinium-234 (²³⁴Pa).
Thorium-231 emits a beta ray characterized by a decay energy of approximately 0.39 MeV.
Answer: True
Explanation: The beta decay of Thorium-231 (²³¹Th) releases energy amounting to approximately 0.39 MeV.
The decay chain originating from Thorium-232 terminates with the stable isotope Lead-207.
Answer: False
Explanation: The decay chain of Thorium-232 (²³²Th), known as the thorium series, concludes with the stable isotope Lead-208 (²⁰⁸Pb), not Lead-207.
Within the Thorium-232 decay chain, isotopes such as Radium-228 and Thorium-228 possess half-lives exceeding one week.
Answer: True
Explanation: Radium-228 (²²⁸Ra) has a half-life of 5.75 years, and Thorium-228 (²²⁸Th) has a half-life of 1.91 years, both significantly longer than one week.
Thorium-234 is an infrequent decay product of Uranium-238, predominantly generated via spontaneous fission.
Answer: False
Explanation: Thorium-234 (²³⁴Th) is a common and direct decay product of Uranium-238 (²³⁸U) through alpha decay, not a rare product formed by spontaneous fission.
The '4n' classification denotes decay chains where the mass number (A) is a multiple of 4.
Answer: True
Explanation: The '4n' classification denotes decay chains where the mass number (A) is a multiple of 4. The decay chain originating from Thorium-232 (²³²Th) belongs to this classification.
What is the approximate half-life of Thorium-232 (²³²Th)?
Answer: 1.40 x 10¹⁰ years
Explanation: The isotope Thorium-232 (²³²Th) possesses a half-life of approximately 1.40 x 10¹⁰ years, a timescale significantly exceeding the age of the Earth and the universe.
Among the provided options, which Thorium isotope exhibits the longest half-life?
Answer: Thorium-232 (²³²Th) - 1.40 x 10¹⁰ years
Explanation: Thorium-232 (²³²Th) possesses the longest half-life among the listed isotopes, at approximately 1.40 x 10¹⁰ years.
What is characteristic of the half-lives for the majority of thorium's radioactive isotopes?
Answer: They are shorter than thirty days, with most under ten minutes.
Explanation: The majority of thorium's radioactive isotopes exhibit short half-lives, typically less than thirty days, and often under ten minutes.
Thorium-231 (²³¹Th) originates from the decay of which uranium isotope, and subsequently decays into which protactinium isotope?
Answer: Uranium-235, Protactinium-231
Explanation: Thorium-231 (²³¹Th) originates from the decay of Uranium-235 (²³⁵U). Upon undergoing beta-minus emission, it transforms into Protactinium-231 (²³¹Pa).
Thorium-233 (²³³Th) decays into Protactinium-233 (²³³Pa), which subsequently leads to Uranium-233 (²³³U) and joins which decay series?
Answer: The Neptunium series
Explanation: The decay sequence starting with Thorium-233 (²³³Th) leads to Uranium-233 (²³³U) and is part of the neptunium series, not the thorium or uranium series.
Thorium-234 (²³⁴Th) is a direct decay product originating from which isotope?
Answer: Uranium-238 (²³⁸U)
Explanation: Thorium-234 (²³⁴Th) is a direct decay product of Uranium-238 (²³⁸U).
What is the ultimate stable product of the Thorium-232 (²³²Th) decay chain?
Answer: Lead-208 (²⁰⁸Pb)
Explanation: The decay chain originating from Thorium-232 (²³²Th), known as the thorium series, terminates with the stable isotope Lead-208 (²⁰⁸Pb).
Excluding Thorium-232 (²³²Th) itself, which isotopes within its decay chain possess half-lives exceeding one year?
Answer: Radium-228 (5.75 yr) and Thorium-228 (1.91 yr)
Explanation: Within the Thorium-232 decay chain, Radium-228 (²²⁸Ra) with a 5.75-year half-life and Thorium-228 (²²⁸Th) with a 1.91-year half-life are the isotopes, besides ²³²Th, that have half-lives exceeding one year.
What is the half-life of Thorium-229 (²²⁹Th)?
Answer: 7,916 years
Explanation: Thorium-229 (²²⁹Th) possesses a half-life of approximately 7,916 years.
Which of the following Thorium isotopes exhibits a half-life measured in minutes or seconds?
Answer: Thorium-233 (²³³Th)
Explanation: Thorium-233 (²³³Th) has a half-life of approximately 21.83 minutes, placing it in the category of isotopes with half-lives measured in minutes or seconds, unlike the others listed.
In 2013, the International Union of Pure and Applied Chemistry (IUPAC) reclassified thorium as binuclidic, a determination prompted by the discovery of significant quantities of Thorium-230 in deep seawater.
Answer: True
Explanation: The reclassification of thorium as binuclidic by IUPAC in 2013 was a direct consequence of the discovery of substantial amounts of Thorium-230 (²³⁰Th) in deep seawater, indicating a more complex natural isotopic composition.
The isotope Thorium-230 was historically designated as 'Actinium X'.
Answer: False
Explanation: The historical designation 'Actinium X' refers to Radium-223 (²²³Ra), a decay product in the actinium series. Thorium-230 (²³⁰Th) was historically known as Ionium (Io).
Within the thorium fuel cycle, Thorium-232 functions as a fertile material, enabling the production of Uranium-233.
Answer: True
Explanation: Thorium-232 (²³²Th) is a fertile nuclide that can absorb neutrons to transmute into Uranium-233 (²³³U), a fissile material crucial for the thorium fuel cycle.
Thorotrast, a suspension of Thorium-232 dioxide, was historically employed as a contrast medium and is presently regarded as non-carcinogenic.
Answer: False
Explanation: Thorotrast, a suspension of Thorium-232 dioxide, was indeed used as a contrast medium; however, it is now recognized as a carcinogen due to the long-term retention of radioactive material within the body.
Thorium-228 is utilized in oncological treatments through alpha particle radiation therapy.
Answer: True
Explanation: Thorium-228 (²²⁸Th), along with its decay product Radium-224 (²²⁴Ra), is employed in medical applications for cancer treatment utilizing alpha particle radiation therapy.
Thorium-229 serves as a precursor for the generation of the medical isotopes Actinium-224 and Bismuth-213.
Answer: False
Explanation: Thorium-229 (²²⁹Th) is a source for producing the medical isotopes Actinium-225 (²²⁵Ac) and Bismuth-213 (²¹³Bi), not Actinium-224.
Thorium-230 finds application in uranium-thorium dating methodologies, particularly for materials such as ancient pottery.
Answer: False
Explanation: While Thorium-230 (²³⁰Th) is crucial for uranium-thorium dating, its primary application in this context is for dating materials like corals and speleothems, not typically ancient pottery, which is more commonly dated using other methods.
The inclusion of thorium in Kodak Aero-Ektar lenses served to enhance optical characteristics such as refractive index and dispersion.
Answer: True
Explanation: Thorium was incorporated into the glass of Kodak Aero-Ektar lenses to leverage its properties of high refractive index and low dispersion, thereby improving optical performance.
What specific discovery prompted the IUPAC to reclassify thorium as binuclidic in 2013?
Answer: The discovery of large quantities of Thorium-230 in deep seawater.
Explanation: The reclassification of thorium as binuclidic by IUPAC in 2013 was based on the discovery of substantial quantities of Thorium-230 (²³⁰Th) in deep seawater.
What historical designation was assigned to Thorium-230 (²³⁰Th)?
Answer: Ionium (Io)
Explanation: The isotope Thorium-230 (²³⁰Th) was historically identified by the name Ionium (Io).
Within the domain of nuclear energy, what specific role is fulfilled by Thorium-232 (²³²Th)?
Answer: It is a fertile material that can be converted into fissile Uranium-233.
Explanation: Thorium-232 (²³²Th) serves as a fertile material in the thorium fuel cycle, wherein it absorbs neutrons to produce the fissile isotope Uranium-233 (²³³U).
What historical medical application involved Thorotrast, a suspension containing Thorium-232?
Answer: As a contrast medium for X-ray diagnostics.
Explanation: Historically, Thorotrast, a suspension of Thorium-232 dioxide, was utilized as a radiopaque contrast medium for diagnostic X-ray imaging.
Which medical isotopes are primarily generated through the decay pathway of Thorium-229 (²²⁹Th)?
Answer: Actinium-225 and Bismuth-213
Explanation: Thorium-229 (²²⁹Th) serves as a primary source for the production of the medical isotopes Actinium-225 (²²⁵Ac) and Bismuth-213 (²¹³Bi).
Thorium-230 (²³⁰Th) is utilized in which scientific dating methodology, with particular relevance for the dating of corals?
Answer: Uranium-Thorium dating
Explanation: Thorium-230 (²³⁰Th) is employed in dating methodologies, notably uranium-thorium dating, which is applied to materials such as corals and is also used for studying ocean current dynamics.
What specific optical property conferred by thorium-containing glasses made them desirable for Kodak Aero-Ektar lenses?
Answer: High refractive index and low dispersion.
Explanation: Thorium-containing glasses were favored for Kodak Aero-Ektar lenses due to their advantageous combination of a high refractive index and low optical dispersion, enhancing lens performance.
To which thorium isotope was the historical designation 'Radiothorium' applied?
Answer: Thorium-228 (²²⁸Th)
Explanation: The historical name 'Radiothorium' was assigned to Thorium-228 (²²⁸Th), owing to its occurrence within the disintegration chain of Thorium-232 (²³²Th).
The nuclear isomer of Thorium-229 (²²⁹mTh) is characterized by an extremely high excitation energy, rendering it unsuitable for precise measurements.
Answer: False
Explanation: The nuclear isomer ²²⁹mTh is notable for its remarkably *low* excitation energy, which facilitates precise measurements and enables potential applications in fields like nuclear clocks.
The excitation energy of the ²²⁹mTh isomer is excessively high, precluding its potential control via laser manipulation.
Answer: False
Explanation: The excitation energy of the ²²⁹mTh isomer is remarkably low (approximately 8.355 eV), which is precisely what makes it a candidate for laser control and applications such as nuclear clocks.
The decay lifetime of the ²²⁹mTh isomer remains unaltered by variations in its electronic environment.
Answer: False
Explanation: The electronic environment critically affects the ²²⁹mTh isomer's decay lifetime, particularly influencing the rate of internal conversion.
The ²²⁹mTh isomer holds potential for applications such as quantum computing qubits and the development of highly accurate nuclear clocks.
Answer: True
Explanation: Due to its exceptionally low excitation energy and potential for laser control, the ²²⁹mTh isomer is considered a promising candidate for quantum computing qubits and highly precise nuclear clocks.
The precise measurement of the ²²⁹mTh isomer's energy has consistently been straightforward owing to its high energy.
Answer: False
Explanation: Precise measurement of the ²²⁹mTh isomer's energy has historically been challenging precisely because of its *low* excitation energy, not high energy.
Highly precise measurements of the ²²⁹mTh transition energy have been achieved through recent experiments utilizing laser spectroscopy on Th⁴⁺ cations.
Answer: True
Explanation: Recent experimental work, including studies from 2024, has employed laser spectroscopy on Th⁴⁺ cations to obtain highly precise measurements of the ²²⁹mTh transition energy.
The nuclear isomer ²²⁹mTh is notable for which characteristic?
Answer: Remarkably low excitation energy, suitable for laser interaction.
Explanation: The ²²⁹mTh isomer is distinguished by its exceptionally low excitation energy, which makes it amenable to laser interaction and potential applications in precision timing and quantum information processing.
The extremely low excitation energy of the ²²⁹mTh isomer holds significance for potential applications in which domains?
Answer: Highly accurate atomic clocks and quantum computing.
Explanation: The low excitation energy of the ²²⁹mTh isomer makes it a promising candidate for developing highly accurate atomic clocks and for use as qubits in quantum computing.
In what manner does the electronic environment influence the decay characteristics of the ²²⁹mTh isomer?
Answer: Internal conversion is inhibited in Th⁺ ions, leading to a longer radiative decay lifetime.
Explanation: The electronic environment critically affects the ²²⁹mTh isomer's decay. In Th⁺ ions, internal conversion is suppressed, resulting in a significantly prolonged radiative decay lifetime compared to neutral atoms.
What is the approximate excitation energy value of the ²²⁹mTh nuclear isomer?
Answer: Approximately 8.355 eV
Explanation: The excitation energy of the ²²⁹mTh nuclear isomer has been determined to be approximately 8.355 eV.
The photons emitted during the decay of the ²²⁹mTh isomer fall within which spectral range, rendering them incapable of propagating through air?
Answer: Vacuum Ultraviolet (VUV)
Explanation: The photons emitted during the decay of the ²²⁹mTh isomer fall within the vacuum ultraviolet (VUV) spectral range. This is attributed to the excitation energy (approximately 8.355 eV) exceeding the VUV cutoff, preventing photon propagation through air.