A modified ionic model is applied to selected actinide thermodynamic measurements to allow the evaluation of gas-phase ion thermodynamics across the actinide series. These are used to predict the thermodynamic properties of a number of actinide compounds and aquo ions at 298.15 K. General guidelines are offered for predicting the relative stabilities of actinide(II), -(III), and -(IV) compounds in various chemical environments.
IntroductionThis paper continues our investigation of the thermodynamic properties of the actinide elements and their These properties are of paramount importance to the nuclear industry, and their variations across the actinide series are of considerable theoretical interest. Therefore, simple and reliable methods of thermodynamic prediction are valuable contributions to actinide research. In previous we have developed a modified ionic model which allows the prediction of the thermodynamic properties of simple lanthanide compounds and ions. In the present work we apply our model to the actinides. Our modified ionic model allows the prediction of the standard enthalpy of formation (A&') of a solid lanthanide compound from a simple equation which is fit to the available AHf' data. The following numerical quantities must be known: the standard enthalpy of formation of the monatomic gas (AHfo(M,g)), the ionization potential sum for the oxidation state under consideration (CfIP(M)), the crystal ionic radius of the metal for coordination number 6 (rMl+), and the correlation parameters for the compound type (halide, oxide, or ~u l f i d e ) .~ We have also given equations for the prediction of the thermodynamic properties of aquo ions
In an attempt to establish the role of the laboratory in chemistry instruction, an historical perspective is developed, in the hope of extracting the consensus of commentators on the subject concerning the important features of the laboratory experience. We present arguments to support the idea that laboratory instruction involves student experiences that mimic what chemists do. We discuss possible techniques to formalize (i.e., in a standard classroom setting) the research experience.
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