Cesium ionic crystal radius

The ionic radius of cesium (1.69 A) is near that of benzene (1.39 A from center to the carbon atoms or 2.47 A to the hydrogen atoms) and the cyclohexa-l,3-dienyI radical hence extensive electrostatic interaction is anticipated between the corresponding anions on intimate contact with cesium cations. Such similarity in size may facilitate close packing in the crystal lattice cesium benzenide appears to be very insoluble in tetrahy-drofuran. 

In 1973, Mikheev et al. reported that a stable, monovalent Md ion could be produced in ethanol solutions and that it co-crystallized with CsQ [45]. However, Samhoun and co-workers studied the overall reduction of Md to the amalgam using controlled potential electrolysis they concluded that Md could not be considered a cesium-like element and no evidence was obtained consistent with a monovalent state [46,47]. Hulet et al. have recently repeated some of the co-crystallization experiments of Mikheev and performed a series of new experiments in an attempt to prepare Md by reduction with Sm in ethanol solutions and also in fused KQ media [37]. In these experiments, the behavior of Md was compared to tracer amounts of 3-i-, 2-i-, and 1-i-ions and Md consistently followed the 2 -i- ions. They concluded that Md cannot be reduced to a monovalent state with Sm as daimed by Mikheev. However, on the basis of the results of thermodynamic studies of the co-crystallization process of mendelevium with chlorides of alkali metals, the Russian investigators maintain that Md can be reduced to the monovalent state in water-ethanol solutions and that the co-crystallization of Md with salts of divalent ions can be explained as being due to the formation of mixed crystals [102,103]. An ionic radius of 1.17 A was calculated for Md from the results of the co-crystallization studies [104]. 

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