![]() In still lower oxidation states, niobium and tantalum give a number of (frequently nonstoichiometric) cluster compounds which can be considered to involve fragments of the metal lattice. However in the -t-4 state, tantalum fails to form a fluoride and neither metal produces a trifluoride. Niobium and tantalum, on the other hand, form all the halides in the high oxidation state, and are in fact unique (apart only from protactinium) in forming pentaiodides. Vanadium(V) is only represented at present by the fluoride, and even vanadium(IV) does not form the iodide, though all the halides of vanadium(III) and vanadium(II) are known. ![]() These are illustrative of the trends within this group which have already been alluded to. The known halides of vanadium, niobium and tantalum, are listed in Table 22.6. It seems likely that in all these reduced oxide phases there is extensive metal-metal bonding. įinally, oxygen is soluble in metallic titanium up to a composition of TiOo.s with the oxygen atoms occupying octahedral sites in the hep metal lattice distinct phases that have been crystallographically characterized are TieO, TisO and Ti20. These compounds are usually opaque, very hard, chemically inert, refractory materials with metallic lustre and conductivity and sometimes having variable composition. The most extensive group of nitrides are the metallic nitrides of general formulae MN, M2N, and M4N in which N atoms occupy some or all of the interstices in cubic or hep metal lattices (examples are in Table 11.1, p. In the latter, which comprise a large group of chemical compounds, complex hydridic anions such as BH, A1H, and derivatives of these, exist. In the former, the negative hydrogen is bonded ionicaHy or covalendy to a metal, or is present as a soHd solution in the metal lattice. Hydrides may be either simple binary compounds or complex ones. Hydrides are compounds that contain hydrogen (qv) in a reduced or electron-rich state. Neutrons usually have not been detected in cold fusion experiments, so that the D-D fusion reaction familiar to nuclear physicists does not seem to be the explanation for the experimental results, which typically involve the release of heat and sometimes gamma rays. ![]() These results have proven extremely difficult to confirm (20,21). The process, referred to as cold fusion, consists of loading deuterium into pieces of palladium metal by electrolysis of heavy water, E)20, thereby developing a sufficiently large density of deuterium nuclei in the metal lattice to cause fusion between these nuclei to occur. In the spring of 1989, it was announced that electrochemists at the University of Utah had produced a sustained nuclear fusion reaction at room temperature, using simple equipment available in any high school laboratory. Therefore, these compounds are represented by individual polyhedral coordination of the ligands such as the octahedron or tetrahedron Figure 2-124d). It is often difficult to represent inorganic compounds with the usual structure models because these structures are based on complex crystals space groups), aggregates, or metal lattices. Thus we can see the change from non-metal to metal in the physical structure of these elements, occurring with increasing atomic weight of the elements carbon, silicon, germanium, tin and lead. Lead has only one form, a cubic metallic lattice.
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