Molecules Containing N, C, and

and O2.—Considerable success has resulted from the application of sophisticated techniques to the study of these small molecules. Changes of morphology on Pt single crystal spheres have been observed during oxidation of NH3, CaHs, and CO. A weakly bound state appears in N2 adsorption on Fe(lll), but not on Fe(lOO), and there are similarities observed between N on Fe(lOO) at 6 0.5, and Fe4N. Reconstruction of Fe(lll) occurs on covering the surface with N and this can be related to work by Boudart et al, on small particles. N2 weakly bound states have been observed for polycrystalline Fe and Kishi and Roberts have related this to the mechanism of adsorption and dissociation. No evidence for weakly bound N2 on Pt(lll) at r 165 K has been found. 

In NH3 oxidation over Pt/Rh catalyst deactivation has been ascribed to Pt loss as oxide.  

The NO + H2 reaction on polycrystalline Pt has been examined as has NO chemisorption and decomposition on Ru. NO and O2 have been studied on Pd(lll) where NO creates, by a virtual pressure route, a surface PdO. On Ir(100)-(5 X 1) NO adsorption has been revealed as molecular at 0 0.1, 

There is conflict over the results of adsorption of O2 on Pt a recent paper points to saturation coverage at 0 = 0.5 on stepped Pt and on Pt(lll). In the CO + O2 system a form of unreactive O has been identified on Pt. In the CO + O2 reaction on Pd a transient form of CO was identified. The role of steps in the CO + O2 reaction has been established as important on Pt where several stepped surfaces were prepared on a Pt single crystal cylinder. 

Zhdan et al. ° have found an unreactive form of O on Ir(l 11) even at 1100 K, and have gone on to study the steady-state oxidation on this surface, establishing a Langmuir-Hinshelwood mechanism for reaction between chemisorbed O and chemisorbed CO. Two forms of adsorbed O on Ir(lll) have also been identified by Ivanov et al., only one of which is active in CO oxidation. 

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Net atomic charges based on the stockholder partitioning of theoretical densities for a number of linear molecules containing N, C, and H are listed in Table 6.1. For these molecules, the charge transfer between atoms is relatively small. Much larger values are obtained for more electronegative atoms, such as oxygen and fluorine bonded to carbon atoms. 

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