Potassium interatomic distance

In other crystals an octahedral metal atom is attached to six non-metal atoms, each of which forms one, two, or three, rather than four, bonds with other atoms. The interatomic distance in such a crystal should be equal to the sum of the octahedral radius of the metal atom and the normal-valence radius (Table VI) of the non-metal atom. This is found to be true for many crystals with the potassium chlorostannate (H 61) and cadmium iodide (C 6) structures (Table XIB). Data are included in Table XIC for crystals in which a tetrahedral atom is bonded to a non-metal atom with two or three covalent bonds. The values of dcalc are obtained by adding the tetrahedral radius for the former to the normal-valence radius for the latter atom. 

Solution X-ray diffraction measurements for saturated aqueous solutions of the KCl-MgCl2-6H20 and CsCl-MgCl2-6H20 double salts at 25°C reveal that magnesium(II) ions in the solutions are fully hydrated as [Mg(H20)6]2+ with a Mg-0 bond length of 208-209 pm. This is essentially the same bond length as in the double salt crystals, and the K+ and Cs+ ions have both water molecules and chloride ions in their first coordination sphere. The coordination numbers for water molecules and chloride ions around a K+ ion are 4.7 and 2.4, respectively, and those around a Cs+ ion are 4.7 and 2.0, respectively. The K+-OH2 and K+-C1 interatomic distances are found to be 227 and 320 pm, respectively, and the Cs+-OH2 and Cs + -Cl distances are 315 and 339 pm, respectively (58). The interatomic distances determined are essentially the same as those that have been reported in the literature for aqueous solutions of potassium and cesium salts. 

Potassium tetrafluoroargentate(III) was first described by Hoppe in 1957 [17]. It was synthesized by fluorination of mixtures of binary nitrates or halides. Hoppe and Homann [18] established from powder data that the interatomic distance in the square anion AgF4 is 1.90 A. At approximately the same time Edwards et al. [19] also reported a preparation of KAgF4 and their unit cell (also from the powder data), was in good agreement with that of Hoppe and Homann. 

When potassium is deposited on the (111) crystal face of rhodium, the work function of the metal decreases markedly. At 20% monolayer coverage, the work function change attains its minimum value of —1.8 eV. If the Rh—K interatomic distance is 1.2 A, what is the charge transfer at the adsorption site of the alkali metal ... 

Hawthorne and coworkers. However, the interatomic distances of Cs to the carborane cages are such that it could be regarded as a cesium-carborane complex in which some degree of interaction exists between the metal and the 7C-electron density on the carborane cage. Since this cesium compound can also be prepared by an ion-exchange reaction directly from lithium, sodium or potassium salts of the C B -cage (see Figure 6b), further study of this and related compounds in solvent extraction of radioactive cesium metal ( Cs) from nuclear waste is envisioned. 

We may well expect that the strongest bonds would have the shortest interatomic distances, and it is accordingly not surprising that the large interatomic distances shown in Figure 17-2 are those for soft metals, such as potassium the smallest ones, for chromium, iron, nickel, and others, refer to the strong, hard metals. 

Tables 2.1-2.4 relative to sodiiun, lithium, potassium, rubidium, and cesium salts, also show that, in general, the values of a obtained by fitting experimental data of activity coefficients are larger than the sum of ionic radii in solutions (or crystal-lattice spacing) and the interatomic distances, d. Also they are close to the values obtained from Kielland sdata and toab initio values calculated by using two models model I and model II, considering the absence and the presence of five water molecules between anion and cation, optimized in the gas phase, respectively), and also to those obtained fi om MM studies, where no water molecules are consid-...

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