ChemInform Abstract: THERMODYNAMIC PROPERTIES OF 5F ELEMENTS

Lanthanides / Actinides / Redox properties / Hydration / CovalenceSummary. The existence of low oxidation states of lanthanides and actinides in aqueous solution has been reexamined in the light of recent data. The retained redox data corresponding to the 3 + /2+ couples are given, and earlier reports of the existence of monovalent mendelevium is not confirmed. By comparing divalent, trivalent and tetravalent ions, the effective charges of the lanthanide and actinide ions have been quantified. It is shown, based on experimental EXAFS data, and modelling of the aquo ions, that the covalent effect in these series increases with the oxidation state, is larger for actinides than for lanthanides and maximum for trivalent and tetravalent ions at the beginning of the series and, in each case, becoming negligible around the middle of the series. For divalent ions this covalent effect is small and constant through the series. Characteristics of the ions have been evaluated and hydration properties deduced.

Section: Existence Of Low Oxidation States Of Lanthanides and Actinidmentioning

confidence: 98%

About low oxidation states, hydration and covalence properties of f elements

David¹

2008

“…But its direct production by Cm(III) oxidation is difficult due to the high potential of the Cm(IV)/Cm(III) pair [151,152]. The stability of +2 state of oxidation on the whole increases with rising TPE atomic number [151], and the Fm(III)/Fm(II) pair has the same oxidation potential as the Yb(III)/Yb(II) pair [153], It has been shown [154] that Fm(III) can be reduced to Fm(II) by electrolysis on mercury cathode.…”

Section: Isotopes and Their Propertiesmentioning

confidence: 99%

Recent Analytical Chemistry of the Transplutonium Elements

Myasoedov¹

1983

The modern state of the analytical chemistry of the transplutonium elements (TPE) ranging from Americium to Lawrencium are reviewed. The main characteristics of the most important isotopes are given, and properties of metals and oxides are discussed. Special attention is paid to the TPE properties in unusual oxidation states in solutions, the methods of production and stabilization, and current methods of isolating and separating of these elements. In conclusion the principal methods of determining TPE and impurities in them are considered.

“…For example, the shift for trivalent actinides from non-complexing to citrate media should be -200 mV for a reversible reaction (p = 2 and log β = 12 [9]). The observed shift (see Cf and Es results in Table 1) is larger than -300 mV, indicating an irreversible reaction [10],…”

Section: Resultsmentioning

confidence: 94%

Electrochemical Reduction and Related Thermodynamic Properties of Nobelium

David

Samhoun²,

Lougheed

et al. 1990

Self Cite

Nobelium / Electrochemistry / Polarography / Thermodynamic properties / Redox potentials SummaryWe have measured the amalgamation potential of nobelium in the presence of both weak (acetate) and strong (citrate) complexing agents using radiocoulometry with the nuclide 259 No. We found that reduction of No occurs through a reversible 2->0 process with a half-wave potential of -1.47+0.01 V versus the standard hydrogen electrode for the amalgamation reaction No 2 + ->No(Hg). We estimate a potential of -2.49 ± 0.06 V for the No 2+ /No couple and review and estimate other thermodynamic properties of nobelium.