Molecular high-temperature species

ANDREWS Using Metal Atoms Molecular High-Temperature Species 159... 

ANDREWS Using Meted Atoms 8 Molecular High-Temperature Species 169... 

High-temperature species are not only identified by their vibrational spectra entropies, force fields, and molecular geometries can also be determined, particularly for small molecules (e.g., transition-metal halides MX2,...). 

Boron suboxides have boron oxygen mole ratios equal to or greater than one. These compounds range from molecular species to refractory solid-state materials. Monomeric vapor-phase BO and B2O2 have been studied by spectroscopic techniques. In addition to these rather unstable high-temperature species, several forms of solid noncrystalline boron suboxides have been reported. A water-soluble low-temperature form is obtained by the vacuum dehydration of tetrahydroxydiborane at 220°C (equation 5). At 500 °C, this form converts to a light brown modification that has also been obtained by reactions of boric oxide with elemental boron, boron carbide, or carbon at high temperatures (>1250 °C). 

In an ionizing solvent, the metal ion initially goes into solution but may then undergo a secondary reaction, combining with other ions present in the environment to form an insoluble molecular species such as rust or aluminum oxide. In high-temperature oxidation, the metal ion becomes part of the lattice of the oxide formed. 

There is little new to be said about the bonding capacity of a lithium atom. With just one valence electron, it should form gaseous molecules LiH and LiF. Because of the vacant valence orbitals, these substances will be expected only at extremely high temperatures. These expectations are in accord with the facts, as shown in Table 16-1, which summarizes the formulas and the melting and boiling points of the stable fluorides of the second-row elements. In each case, the formula given in the table is the actual molecular formula of the species found in the gas phase. 

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