Chemical properties of positive singly charged astatine ion in aqueous solution

Milanov, M.; Doberenz, V.; Khalkin, V.A.; Marinov, A.

doi:10.1007/bf02037143

Cited by 18 publications

(11 citation statements)

References 3 publications

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“…It may be so that we failed to take into account all the factors slowing down the At(0) + electromigration in aqueous solutions, and thus the true value of K. is smaller than the one deterdp mined in the paper. Nevertheless, it is almost three orders of magnitude smaller than those calculated earlier for (H 2 0) n I + [4] and (H 2 0) n At + [16], which agrees with the idea that the cation of the fifth halogen is more stable in aqueous solutions than cations of other elements in this group with respect to the hydrolysis reactions.…”

Section: (3)supporting

confidence: 90%

“…Actually, the experiment confirmed the assumption: the astatine mobility was found to be reduced from +2.67 • 10 -4 to + 1.17 • 10 -4 cm 2 V -1 s -1 when the pH changed from 0.6 to 1.7 in solutions of H(Na)C10 4 -K 2 Cr 2 0 7 with the ion force μ = 0 4, 25 °C [16]. The deprotonation constant calculated for (H 2 0) n At + turned out to be nearly the sameasthatof(H 2 0) n I + [4]: Kdp = 3.2(5)· 10 -2 molel -1 .…”

Section: Introductionsupporting

confidence: 83%

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Investigation of Astatine Cation Electromigration

et al. 1989

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Electromigration of astatine ( 210 ' 2 " At) has been investigated in aqueous solutions of 0.25 mole I" 1 H(Na)C10"+5 • 10" 3 mole Γ 1 K 2 Cr 2 0, orNa 2 S 2 0, at 25°C, 0.7 < pH < 10.4. Like K 2 Cr 2 0,, Na 2 S 2 0" seems to oxidize astatine only to At(0) + , i. e. to an univalent cation, probably being protonized hypoastatine acid (H 2 0) n At + . The literature data on oxidation of astatine by Na, S 2 0 8 to At 3+ (AtO + ) were not confirmed. The mean mobility of the At(©) + cation is well described by the empiric equation _ = "At(Q) + (1 + *" dp ·«"'+)-(1+6 pH) where = 7.6(3.0)· 10" 5 molel" 1 is the deprotonation constant of (H 2 0) n At + , δ =0.18; "ΑΙ(Θ) + =+3.80(5) Χ ΙΟ" 4 cm 2 V"' s" 1 . In solutions of K 2 Cr 2 0 7 with pH > 1.7 and in solutions without oxidation agents At(0) + is unstable and is converted to a neutral form, probably, At 0 .

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Section: (3)supporting

confidence: 90%

Section: Introductionsupporting

confidence: 83%

Investigation of Astatine Cation Electromigration

et al. 1989

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“…In addition, corresponding hypothetical ions with reversed charges, i.e., Na – , K – , and Rb – ( q I = −1 e) as well as F + and I + ( q I = +1 e), were also considered, with the same ion–water Lennard-Jones interaction parameters as the corresponding physical ions but with opposite charges. The latter ions serve as a test for the effect of anisotropic solvation at constant effective ionic radius, and are not meant to provide realistic models for the corresponding physical (but rather uncommon − ) ions.…”

Section: Computational Detailsmentioning

confidence: 99%

Origin of Asymmetric Solvation Effects for Ions in Water and Organic Solvents Investigated Using Molecular Dynamics Simulations: The Swain Acity–Basity Scale Revisited

Reif

Hünenberger

2016

J. Phys. Chem. B

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The asymmetric solvation of ions can be defined as the tendency of a solvent to preferentially solvate anions over cations or cations over anions, at identical ionic charge magnitudes and effective sizes. Taking water as a reference, these effects are quantified experimentally for many solvents by the relative acity (A) and basity (B) parameters of the Swain scale. The goal of the present study is to investigate the asymmetric solvation of ions using molecular dynamics simulations, and to connect the results to this empirical scale. To this purpose, the charging free energies of alkali and halide ions, and of their hypothetical oppositely charged counterparts, are calculated in a variety of solvents. In a first set of calculations, artificial solvent models are considered that present either a charge or a shape asymmetry at the molecular level. The solvation asymmetry, probed by the difference in charging free energy between the two oppositely charged ions, is found to encompass a term quadratic in the ion charge, related to the different solvation structures around the anion and cation, and a term linear in the ion charge, related to the solvation structure around the uncharged ion-sized cavity. For these simple solvent models, the two terms are systematically counteracting each other, and it is argued that only the quadratic term should be retained when comparing the results of simulations involving physical solvents to experimental data. In a second set of calculations, 16 physical solvents are considered. The theoretical estimates for the acity A are found to correlate very well with the Swain parameters, whereas the correlation for B is very poor. Based on this observation, the Swain scale is reformulated into a new scale involving an asymmetry parameter Σ, positive for acitic solvents and negative for basitic ones, and a polarity parameter Π. This revised scale has the same predictive power as the original scale, but it characterizes asymmetry in an absolute sense, the atomistic simulations playing the role of an extra-thermodynamic assumption, and is optimally compatible with the simulation results. Considering the 55 solvents in the Swain set, it is observed that a moderate basity (Σ between -0.9 and -0.3, related to electronic polarization) represents the baseline for most solvents, while a highly variable acity (Σ between 0.0 and 3.0, related to hydrogen-bond donor capacity modulated by inductive effects) represents a landmark of protic solvents.

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“…In acidic conditions and in the presence of a strong oxidizer, there exists another "metallic" species characterized by a positive charge in electromobility experiments 33 and in ion exchange chromatography. 34 The most frequently suggested chemical forms for species III are At + , At 3+ , and AtO + .…”

Section: I1 Construction Of the Pourbaix Diagrammentioning

confidence: 99%