Bond energies metals

Both atomic and metal oxide ions were observed in initial investigations. Ions with low metal oxide or hydroxide bond energies resulted in the detection of only the bare metal ions. For elements with strong oxide bond energies, metal oxides were observed. By utilizing the preselection capability of the linear quadrupole, it was determined that the metal oxides were not originating from the ion... 

The observation of C-H, Si-H, Si-I, and Si-Si bond activation by Pd(0) and Pt(0) complexes has prompted theoretical studies of Sakaki and coworkers [29] concerning the C-H, C-C, and Si-X (X = H, C, Si, and F) bond activation on the Pt(PH3)2 and Pd(PH3)2 complexes. In these calculations the MP2 and MP4(SDQ) methods with the double-zeta quality basis sets argumented by the polarization d function and ECP for heavier atoms have been used. As shown in Table III, the oxidative addition of C-H and C-C bonds to Pt(PH3)2 is endothermic by 6.5 and 5.2 kcal/mol, respectively, while it is exothermic by 25.6, 28.6, 14.1, and 46.4 kcal/mol for Si-H, Si-F, Si-C, and Si-Si bonds, respectively. These differences in exother-micity of the reaction have been explained in terms of the Pt-X bond energies metal-alkyl bonds are a few kilocalories per mole weaker than the metal-H bond, which in turn is 0-15 kcal/mol weaker than metal-silyl or metal-F bonds. The activation barriers increase via the trend SiH (0.7 kcal/ mol) < SiSi (17.0 kcal/mol) < SiF (26.8 kcal/mol) < SiC (28.1 kcal/mol)... 

Metals A and B form an alloy or solid solution. To take a hypothetical case, suppose that the structure is simple cubic, so that each interior atom has six nearest neighbors and each surface atom has five. A particular alloy has a bulk mole fraction XA = 0.50, the side of the unit cell is 4.0 A, and the energies of vaporization Ea and Eb are 30 and 35 kcal/mol for the respective pure metals. The A—A bond energy is aa and the B—B bond energy is bb assume that ab = j( aa + bb)- Calculate the surface energy as a function of surface composition. What should the surface composition be at 0 K In what direction should it change on heaf)pg, and why ... 

Hydrogen gas chemisorbs on the surface of many metals in an important step for many catalytic reactions. A method for estimating the heat of hydrogen chemisorption on transition metals has been developed (67). These values and metal—hydrogen bond energies for 21 transition metals are available (67). 

Bond energies of gaseous polyvalent metal halides... 

These data also show that the bond energies decrease as the atomic number of the metal increases in the same Group of the Periodic Table. 

Table 2.3 Metal-carbon bond energies for some methyls...

The resulting data for liquid metals indicate a systematic relationship witlr the bonding energy of the element, which is reflected in the heat of vaporization... 

The metallic bond, as the name says, is the dominant (though not the only) bond in metals and their alloys. In a solid (or, for that matter, a liquid) metal, the highest energy electrons tend to leave the parent atoms (which become ions) and combine to form a sea of freely wandering electrons, not attached to any ion in particular (Fig. 4.8). This gives an energy curve that is very similar to that for covalent bonding it is well described by eqn. (4.4) and has a shape like that of Fig. 4.6. 

Si-Si bond energy. The element is a semiconductor with a distinct shiny, blue-grey metallic lustre the resistivity decreases with increase of temperature, as expected for a semiconductor. The actual value of the resistivity depends markedly on purity but is 40ohmcm at 25° for very pure material. 

At the same time, the relatively low energy and ionic character of the chemical bonds between metal and fluorine cause some difficulties in the application of fluoride compounds. First, fluorides typically have a tendency towards thermolysis and hygroscopicity. In addition, fluoride compounds usually display relatively low temperatures of electrostatic and magnetic ordering. 

To end the discussion of octa-, hepta- and hexafluorotantalates (-niobates) of alkali metals, it should be mentioned that indication of the uniformity of bond energy was found using X-ray electronic spectroscopy [172] based on the... 

Bismuth, excess entropy of solution of noble metals in liquid bismuth, 133 Block polymers, 181 Bond energies in the halogens, 61 Boron fluoride as initiator in polymerization, 156... 

This qualitative description of the interactions in the metal is compatible with quantum mechanical treatments which have been given the problem,6 and it leads to an understanding of such properties as the ratio of about 1.5 of crystal energy of alkali metals to bond energy of their diatomic molecules (the increase being the contribution of the resonance energy), and the increase in interatomic distance by about 15 percent from the diatomic molecule to the crystal. 

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