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Chemical Periodicity and the Periodic Table The modern periodic table derives principally from the work of Dimitri Mendeleev, who in 1869 enunciated a " periodic law " that the properties of the elements are a periodic function of their atomic weights and arranged the 65 known elements in a " periodic table. " Fundamentally, every column in the main body of the table is a group of elements that display similar chemical and physical behavior. Similar properties are therefore exhibited by elements with widely different masses. Chemical periodicity is central to the study of chemistry, and no other generalization comes close to its ability to systematize and rationalize known chemical facts. With the development of atomic theory and an understanding of the electronic structure of atoms, chemical periodicity and the periodic table now find their natural explanation in the electronic structure of atoms. Moving from left to right along any row, the elements are arranged sequentially according to nuclear charge (the atomic number). Electrons balance that charge, hence each successive element has one more electron in its configuration. The electron configuration, or distribution of electrons among atomic orbitals, may be determined by application of the Pauli principle (paired spin in the same orbital) and the Aufbau principle (which outlines the order of filling electrons into shells of orbitals s, p, d, f, etc.) such that in a given atom, no two electrons may have all four quantum numbers identical.
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F ew people have ever seen plutonium, and far fewer have actually handled or manipu-lated it. Yet this manmade element has arguably altered the course of civilization as much as copper, bronze, iron, or steel. Within five years of its synthesis, the primary use of plutonium was for the release of nuclear energy in weapons of mass destruction, and i...
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... Recent advances in heavy element chemistry spurred by innovative molecular design, new spectroscopic techniques, and relativistic theory have evolved our understanding of the divergence between the chemistries of 5f elements and their 4f counterparts. Historically, the primary distinction between these two series has been that early actinides display facile redox chemistry compared to lanthanides, with the exception of those with special electronic configurations such as Eu II (4f 7 ) and Yb II (4f 14 ) 1 . This key attribute is largely lost in all trans-plutonium elements (excluding nobelium) where the most stable oxidation state is 3+, akin to lanthanides 2 . ...
The actinides, from californium to nobelium (Z = 98–102), are known to have an accessible +2 oxidation state. Understanding the origin of this chemical behaviour requires characterizing CfII materials, but investigations are hampered by the fact that they have remained difficult to isolate. This partly arises from the intrinsic challenges of manipulating this unstable element, as well as a lack of suitable reductants that do not reduce CfIII to Cf°. Here we show that a CfII crown–ether complex, Cf(18-crown-6)I2, can be prepared using an Al/Hg amalgam as a reductant. Spectroscopic evidence shows that CfIII can be quantitatively reduced to CfII, and rapid radiolytic re-oxidation in solution yields co-crystallized mixtures of CfII and CfIII complexes without the Al/Hg amalgam. Quantum-chemical calculations show that the Cf‒ligand interactions are highly ionic and that 5f/6d mixing is absent, resulting in weak 5f→5f transitions and an absorption spectrum dominated by 5f→6d transitions.
... The most successful for these purposes are those radionuclides that are firmly bound to soil particles. These include technogenic 137 Cs (Squire and Middleton, 1966;Adeleye et al., 1994;Von Gunten and Beneš, 1995;Efremov, 1988;Salbu, 2006Salbu, , 2009Semenkova et al., 2018), various Pu and 241 Am isotopes (Sholkovitz, 1983;Livens and Baxter, 1988;Penrose et al., 1990;Clark, 2000;Hinton and Pinder, 2001;Choppin, 2007;Romanchuk et al., 2016). The correct application of radioisotope techniques is possible if there is confirmed information about the sources of their emissions, the spatial variability of the initial deposition and the characteristics of their behavior in the environment. ...
The purposes of this study are to determine the content and origin of anthropogenic fallout radionuclides (FRN)
in soils of Mount Khuko, located in the western sector of the Caucasus Mountains and to assess the possibility to
use them for evaluation of sediment redistribution for the alpine grasslands,.
The field study was carried out in August 2019 near the top of Mount Khuko, located in the western part of the
main Caucasus Mountain Ridge. Integral and incremental soil samples were collected from the different
morphological units of the studied area. The content of 137Cs and 241Am in soil samples was evaluated using
laboratory gamma-spectrometry. A part of samples was selected for Pu isotopes extraction and then alphaspectrometric analysis.
It was established that the 137Cs contamination of soils in the studied area has at least two sources of origin.
The first source is the 137Cs bomb-derived fallout after the bomb tests in 1950–60th, which is widespread across
the globe. The second source is 137Cs Chernobyl-derived fallout High random variability (Cv = 25–42%) was
found within reference sites, located at the undisturbed areas on the local flat interfluves due to high variability
of soil characteristics (grain size, density, organic matter content etc.). However minimum spatial variability
(range 12,2–14,3 kBq/m2
) was identified for the mean value of 137Cs inventories for all 5 reference sites located
in the different parts of the studied area. It is difficult to separate individual peaks of the bomb-derived and
Chernobyl-derived 137Cs falloutin sediment sinks with low sedimentation rates.
Application 239,240Pu as an additional chronological marker allows to identify the origin of above mention
peaks in the soils of alpine grasslands and of dry lake bottom.
... Tableau 1 : Comparaison des structures électroniques des lanthanides et des actinides (Clark, 2000) Actinide Configuration D'après les configurations électroniques énumérées dans le Tableau 1, les orbitales 6d des actinides semblent énergétiquement plus accessibles que les orbitales 5d des lanthanides, particulièrement au début de la série. Les actinides du début de la série jusqu'à l'américium présentent un comportement et une réactivité plus complexes que ceux des lanthanides car les orbitales 5f sont incomplètes et sont étendues dans l'espace alors que les orbitales 4f des lanthanides sont localisées. ...
... Ces bandes sont plus ou moins intenses selon l'état d'oxydation du plutonium et permettent également de pouvoir le quantifier lorsque leur coefficient d'extinction molaire est connu (Cohen, 1961;Morss et al., 2006). (Clark, 2000) La radioactivité du plutonium est à l'origine de la décomposition radiolytique de l'eau générant des agents d'oxydoréduction assez puissants, notamment des radicaux à courte durée de vie H • , HO • et O • , ainsi que des produits de recombinaison radicalaire tels que H2, O2 et H2O2. (Connick, 1949;Rabideau, 1953). ...
... Chaque état d'oxydation présente une chimie de coordination variée, une réactivité caractéristique et une solubilité des complexes moléculaires spécifique. La chimie du plutonium en solution aqueuse est donc particulièrement complexe et fascinante (Pikaev, Shilov et Gogolev, 1997 (Clark, 2000;Morss et al., 2006). c) Le cas particulier de l'hydrolyse Le comportement hydrolytique des ions plutonium a fait l'objet de nombreuses études. ...
L’utilisation et l’exploitation d’actinides, éléments radioactifs, peuvent engendrer une propagation anthropique dans l'environnement. Ces accumulations et rejets environnementaux soulèvent une multitude de questions concernant l'impact sur l'environnement, la biosphère et la population humaine. Par conséquent, les recherches autour de la toxicité de ces éléments sont devenues un centre d’intérêt majeur. Dans ce cadre de recherche, l'acquisition d'informations structurales sur les complexes d'actinides avec les protéines permet d’améliorer la compréhension des mécanismes biologiques de contamination. Nos études se consacrent avec deux éléments actinides : le plutonium ainsi que sur son analogue thorium (au degré d'oxydation +IV), dont le comportement présente des similitudes avec l'homéostasie du fer. Une première partie de mon travail a eu pour objectif de décrire les modes d'interaction entre Pu/Th et la ferritine qui régule le stockage du fer dans les cellules. La ferritine est composée d’un cœur ferrique d’oxo-hydroxo de Fe(III) entouré d’un anneau protéique. Les mesures XAS (EXAFS) couplées à de la modélisation ont permis d’identifier les interactions entre Pu/Th et la ferritine mais aussi de déterminer la structure des sites de complexation. Le deuxième axe de recherche a porté sur la complexation de Pu/Th par la transferrine dont le rôle est le transport du fer sérique vers les cellules. Les mesures XAS (EXAFS) couplées à de la modélisation ont permis de montrer que Pu/Th(IV) interagissent avec les deux sites de complexation du fer dans la protéine. Dans ces conditions, la modification de la structure tertiaire de la protéine a été analysée par SAXS. Cette dernière parait être en conformation ouverte lorsque deux cations Pu/Th lui sont liés alors que dans le cas du Fe(III) elle adopte une conformation fermée. La conformation de la transferrine (fermée) est essentielle à sa reconnaissance par la protéine réceptrice à la surface cellulaire afin d’y être internalisée.
... -axis in radial distance from the nucleus whereas ( ) radial probability to find an electron at a distance from the nucleus. From [86] 6 CHAPTER 1. GENERAL INTRODUCTION ...
n this thesis, we will study f -electron systems under two different aspects: the formation and the breakdown of lattice coherence, and the nature of f -electrons, which can be either localized, itinerant, or dual. In the first part, we study lattice coherence in 4f systems with the atomic substitution of magnetic atoms by non-magnetic atoms. We will deal with the ubstitutional disorder by using the dynamic mean-field, theory. We start by generalizing the Doniach type phase diagram with substitution by considering the phases: ferromagnetic, antiferromagnetic, and paramagnetic Kondo. We also study the relevance of our phase diagrams by comparing the experimental data of various cerium-based Kondo alloys. Next, we will focus on the Kondo paramagnetic phase on a square lattice in order to study the signatures of lattice coherence breakdown with the dilution of magnetic impurities. To do this, we analyze the photoemission signals, the effective masses, the local potential scattering, and the charge order. We confirmed previous predictions of a Lifshitz-type transition between dilute and dense impurity systems. In addition, we detect a new critical concentration for a Fermi liquid instability. The latter is highlighted by a vanishing effective mass. The second part of this thesis deals with the apparent dual character of 5f electrons in actinide-based heavy-fermion compounds, where itinerant and localized 5f -degrees of freedom seem to coexist. We adopt the rotationally invariant slave-boson method to study the influence of intra-atomic, i. e., Hund’s rule type correlations. Our results confirm the conjecture that intra-atomic correlations may enhance anisotropies in the effective 5f -5f hopping and thus eventually lead to orbital-selective partial localization. Finally, we analyze the different partially localized phases in terms of orbital-dependent quasiparticle mass and occupation, magnetization, and valency configurations.
... T he separation of minor trivalent actinides (An 3+ ) from their lanthanide (Ln 3+ ) counterparts is a crucial step in the reprocessing of spent nuclear fuels; however, this process remains a great challenge owing to similarities in oxidation state and ionic radii [1][2][3] . Despite these resemblances, prominent differences in the bonding of these elements are observed because of the greater radial extension of the 5f shell in the actinides, compared to the 4f shell of the lanthanides [4][5][6] . Covalency is an important aspect of bonding in actinides, largely driven by the hard/soft nature of the ligand and the formal oxidation state of the actinide ion 1,5 . ...
Variations in bonding between trivalent lanthanides and actinides is critical for reprocessing spent nuclear fuel. The ability to tune bonding and the coordination environment in these trivalent systems is a key factor in identifying a solution for separating lanthanides and actinides. Coordination of 4,4′−bipyridine (4,4′−bpy) and trimethylsilylcyclopentadienide (Cp′) to americium introduces unexpectedly ionic Am−N bonding character and unique spectroscopic properties. Here we report the structural characterization of (Cp′3Am)2(μ − 4,4′−bpy) and its lanthanide analogue, (Cp′3Nd)2(μ − 4,4′−bpy), by single-crystal X-ray diffraction. Spectroscopic techniques in both solid and solution phase are performed in conjunction with theoretical calculations to probe the effects the unique coordination environment has on the electronic structure.
... While this plutonyl triscarbonato approach to explaining the EXAFS data was successful, it does not provide a satisfactory chemical explanation for the splitting that we observe in the O eq shell, which would not be expected for such a complex. 10,91 Additionally, our aqueous speciation calculations show that a plutonyl triscarbonato complex is not a major aqueous species in the synthesis conditions. Therefore, additional models were constructed to explore plausible explanations for this discrepancy, assuming that two distinct Pu−O eq shells required two distinct Pu−O eq coordination environments. ...
... The effect of EDTA on Pu(III) sorption to magnetite was investigated as a function of pH (6)(7)(8)(9)(10)(11)(12) on the mineral surface, suggesting that the sorption process involves an oxidation step. ...
... 1b shows that the addition of EDTA shifts the aqueous Pu(III)/Pu(IV) boundary to more oxidizing conditions within a broad pH-range(4)(5)(6)(7)(8)(9)(10)(11)(12)(13), resulting in a larger aqueous Pu(III) predominance region in the presence of EDTA as opposed to in the absence of EDTA. The subsequent addition of calcium to the Pu-EDTA system(Figure B.1c) shifts the aqueous Pu(III)/Pu(IV) boundary to more reducing conditions at pHm ≥ 7, slightly decreasing the aqueous Pu(III) predominance region as compared to the region in the absence of calcium. ...
... 6 shows a comparison of sum area normalized TRLFS spectra at each individual pHm(7)(8)(9)(10)(11)(12) and the background corrected intensity spectra for pHm11 and 12 analyses as a function of calcium concentration. The sum area normalized spectra at each pHm(Figure 4.6a-d) highlight the formation of the Cm(OH)(EDTA) 2complex (606.9 nm) at low calcium concentrations and the Ca-Cm-EDTA complex (603.8 ...
This dissertation explores the behavior of plutonium in the presence of ethylenediaminetetraacetic acid (EDTA) under environmentally- and repository-relevant boundary conditions. There are two main research foci: (i) defining the binary interactions between plutonium and EDTA and (ii) probing the impact of major cations of environmental relevance (Ca(II), Fe(II/III)) on the interactions of plutonium and EDTA. The first area of research utilized undersaturation solubility studies, spectrophotometry, and advanced spectroscopic methods as a function of pH and time to investigate the speciation, solubility, and redox reactions in binary Pu-EDTA systems. The second area of research highlights the role of aqueous Ca(II) and iron oxide minerals within Pu-EDTA systems through the use of undersaturation solubility studies, advanced spectroscopic techniques, theoretical modeling efforts, and ternary sorption studies. The results of this dissertation indicate that the investigation of binary systems is not enough to develop a comprehensive understanding of the fate and transport of plutonium; the interplay between different environmental interactions can significantly impact the long-term mobility of plutonium in environmental settings and must be understood to further waste disposal and remediation/containment efforts.
... Due to the electrochemical properties of Pu, different Pu oxidation states ranging from + III to + VI can co-exist in solution [2,[27][28][29][30] and each of the four states can form various complexes [27] , resulting in several Pu species eluting separately from an ion exchange column [2,27] . For quantitative isotopic analysis, such as isotope ratio measurements, it is preferable to have only one peak for Pu. ...
... Due to the electrochemical properties of Pu, different Pu oxidation states ranging from + III to + VI can co-exist in solution [2,[27][28][29][30] and each of the four states can form various complexes [27] , resulting in several Pu species eluting separately from an ion exchange column [2,27] . For quantitative isotopic analysis, such as isotope ratio measurements, it is preferable to have only one peak for Pu. ...
... Due to the electrochemical properties of Pu, different Pu oxidation states ranging from + III to + VI can co-exist in solution [2,[27][28][29][30] and each of the four states can form various complexes [27] , resulting in several Pu species eluting separately from an ion exchange column [2,27] . For quantitative isotopic analysis, such as isotope ratio measurements, it is preferable to have only one peak for Pu. ...
A method was developed for the determination of the nuclide-specific concentrations of U, Pu, Nd and Gd in two types of spent nuclear fuel (UOx and Gd-enriched). High-performance ion chromatography (HPIC) was used to separate the target elements from one another while sector-field inductively coupled plasma-mass spectrometry (SF-ICP-MS) was used for their determination relying on isotope dilution for calibration. In order to obtain the best possible precision for these isotope ratios extracted from the transient HPIC-SF-ICP-MS signals, the SF-ICP-MS data acquisition parameters were optimized and the most suitable method for calculating the isotope ratios from the transient signals was identified. The point-by-point (PbP), linear regression slope (LRS) and peak area integration (PAI) approaches were compared in the latter context. It was found that data acquisition in the flat centre of the spectral flat top peak using a mass window of 25 %, a dwell time of 10 ms and 20 samples per peak, while using PAI for isotope ratio calculation, gave the best precision on the isotope ratios extracted from the HPIC-SF-ICP-MS transient signals. These parameters were used in the determination of the nuclide-specific mass fractions of Pu, Nd and Gd in two types of spent nuclear fuel using isotope dilution HPIC-SF-ICP-MS. For U, which was present at a higher concentration, the element fraction was collected and analysed off-line after dilution. For the other target elements, an online approach was used. An uncertainty budget estimation was made using the bottom-up approach for the resulting mass fractions, and the accuracy and precision obtained when using isotope dilution HPIC-SF-ICP-MS were compared with those obtained with the routinely used techniques, isotope dilution TIMS & alpha spectrometry (an ISO 17025 accredited method).
... 3 However, it is very difficult to predict the chemical behaviour of plutonium in the environment because plutonium can simultaneously exist in multiple oxidation states (+3, +4, +5, and +6) in a single aquatic system, and aquatic plutonium (bio)geochemistry is exclusively governed by the oxidation state. 4 For instance, tetravalent plutonium, Pu (IV), is considered insoluble and readily adsorbed, but Pu(IV) transport can be facilitated by colloids. However, hexavalent plutonium, Pu(VI), is relatively soluble and behaves as an aqueous species due to its complexation with a variety of inorganic and organic ligands. ...
We present the first experimental evidence for the ternary complexation of calcium and magnesium ions with plutonyl(VI) tricarbonate species in carbonate-containing aqueous solutions using visible-NIR spectrophotometric titration. Prior to studying the ternary plutonyl(VI) carbonate complexation, visible-NIR absorption spectral information of PuO2(CO3)2²⁻ and PuO2(CO3)3⁴⁻ was successfully obtained. PuO2(CO3)2²⁻ has a prominent peak at 853 nm and its molar absorptivity was determined to be ε853, PuO2(CO3)2²⁻ = 49.0 ± 4.2 M⁻¹·cm⁻¹. The spectrophotometric titration results by adding calcium or magnesium to the plutonyl(VI) carbonate system consisting of PuO2(CO3)2²⁻ and PuO2(CO3)3⁴⁻ indicate the formation of CaPuO2(CO3)3²⁻ and MgPuO2(CO3)3²⁻ complexes and provide the formation constants at 0.1 M H/NaClO4 for MPuO2(CO3)3²⁻ from PuO2(CO3)3⁴⁻, log K = 4.33 ± 0.50 and 2.58 ± 0.18 for M = Ca²⁺ and Mg²⁺, respectively. In addition, the formation constants of CaPuO2(CO3)3²⁻ and MgPuO2(CO3)3²⁻ from PuO2(CO3)3⁴⁻ at infinite dilution (log K°) were proposed to be 6.05 ± 0.50 and 4.29 ± 0.18, respectively, based on the correction of ionic strength using the Davies equation. The absorption spectrum of the ternary plutonyl(VI) complexes of CaPuO2(CO3)3²⁻ is similar to that of PuO2(CO3)3⁴⁻ with the exception of a characteristic absorption peak at 808 nm (ε808, CaPuO2(CO3)3²⁻ = 42.9 ± 1.6 M⁻¹·cm⁻¹). According to the calculated aqueous plutonyl(VI) speciation including the ternary plutonyl(VI) complexes, CaPuO2(CO3)3²⁻ is considered the dominant Pu(VI) species under environmental conditions, and plutonyl(VI) may be more mobile than expected in previous assessments.
... Since the first discovery in 1940, plutonium (Pu) promptly became one of the most conspicuous elements in the periodic table owing to its irreplaceable role in the development of weapons, civil nuclear power, and the generation of radioisotope thermoelectric. 1 However, the chemical research on Pu is hindered substantially by synthetic challenges originating from the extreme radio-and chemo-toxicity of its available radioisotopes. 2 In fact, only a handful of chemical laboratories worldwide have attempted to manipulate Pu isotopes, thus, leading to limited knowledge on Pu chemistry, compared with those of transition metals, lanthanides, and even early actinides such as thorium and uranium. 3 Besides, Pu is one of the most chemically complicated elements in the periodic table, predominately due to its unique position in the actinide series where the degeneracy of 5f and 6d orbitals emerges, while 5f electrons are at the transition border between being delocalized and localized. ...
