Potassium oxide coordination number

The oxides and acids of antimony resemble those of arsenic, except that antimony in antimonic acid has coordination number 6, the formula of antimonic acid being HSb(OH)3. A solution of potassium antimonate, K+[Sb(OH)g], finds use as a test reagent for sodium ion sodium antimonate, NaSb(OH)3, one of the very few sodium salts with slight solubility in water (about 0.03 g per 100 g), is precipitated. The. antimonate ion condenses to larger complexes when heated this condensation may ultimately lead to macromolecular structures, such as... 

A Potassium has an ionic radius of 1.5 A compared with lithium at 0.9 A. This difference is reflected in their coordination numbers, where potassium is normally six- or eight-coordinate and lithium is often found to be four-coordinate. For example, lithium oxide forms the antifluorite structure with lithium in the tetrahedral holes ill a close-packed lattice of oxygen ions. 

Potassium fluotitanate, K2TiFe, is a convenient source for the preparation of other titanium salts. It can easily be obtained pure because it is sparingly soluble (0.6 gram in 100 grams of water at 0°), and it is therefore used as a primary standard in oxidation-reduction titrations. Its existence and stability illustrate the power of the fluoride ion to form stable C9mplex ions and to bring out the highest coordination number of an element. 

With the metals of the first transition series, the maximum coordination number of higher oxidation states is six, and this is so firmly fixed that in their fluoride complexes the oxidation state of the metal in question can be fixed by controlling the mol fraction of alkali metal present 26). Thus, the fluorination of a vanadium salt in the presence of a one, two, or three mol ratio of potassium ion, yields KV F6, KgWVFe, or KsV Fe. The same tendency is shown, but to a lesser degree, by metals of the second transition series, as exemplified by KRuFe and KgRuFe. For an unusual example in the third series, note that OsFe is known, OsFt is not stable, but heptavalent osmium is found as six-coordinated OsOFs (27). 

In the crystal structure of potassium oxide, the oxide ions are coordinated by eight potassium ions. What is the coordination number of potassium ... 

The oxidation-number system is easily extended to include other coordination compounds. Even the interesting substances represented by the formulas Na4Ni(CN)4 and K4Pd(CN)4 create no nomenclature problem they become sodium tetracyanonickelate(0) and potassium tetracyanopaHadate(0), respectively. 

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