Oxidation state A concept that provides

Oxidation states A concept that provides a way to keep track of electrons in oxidation-reduction reactions according to certain rules. 

Oxidation-reduction (redox) reaction a reaction in which one or more electrons are transferred. (4.4 4.10 11.1) Oxidation states a concept that provides a way to keep track of electrons in oxidation-reduction reactions according... 

That carbon monoxide could be oxidised in a facile reaction at cryogenic temperature (100 K) was first established in 1987 by XPS at an aluminium surface.21 The participation of reactive oxygen transients O 1 (s) was central to the mechanism proposed, whereas the chemisorbed oxide O2 state present at 295 K was unreactive. This provided a further impetus for the transient concept that was suggested for the mechanism of the oxidation of ammonia at a magnesium surface (see Chapter 2). Of particular relevance, and of crucial significance, was Ertl s observation by STM in 1992 that oxygen chemisorption at Al(lll) resulted in kinetically hot adatoms (Figures 4.1 and 4.7). 

In subsequent research, it turned out that two-state reactivity can also provide a concept for the understanding of oxidation reactions way beyond the scope of gas-phase ion chemistry and can actually resolve a number of existing mechanistic puzzles. In enzymatic oxidations involving cytochrome P450, for example, changes in spin multiplicity appear to act as a kind of mechanistic distributor for product formation [27-29], and in the case of manganese-catalyzed epoxidation reactions, two-state scenarios have been put forward to account for the experimentally observed stereoselectivities [30-32], Two-state reactivity is not restricted to oxidation reactions, and similar scenarios have been proposed for a number of other experimentally studied reactions of 3d metal compounds [33-37]. Moreover, two-state scenarios have recently also been involved in the chemistry of main group elements [38]. The concept of two-state reactivity developed from the four-atomic system FeO /H2... 

The concept of an atom s oxidation state see Oxidation Number) can provide fundamental information about the stmcture and reactivity of the compound in which the atom is found. In fact, it can be argued that oxidation states provided the basis for Medeleev s initial organization of the periodic table. For the main group elements, the relative stability of lower oxidation states within a given group increases as the atomic number increases. This trend in the periodic table see Periodic Table Trends in the Properties of the Elements) is generally attributable to the presence of an inert s pair see Inert Pair Effect) caused by relativistic effects see Relativistic Effects). 

On the other hand, there are good reasons for believing that this is not always the case and with, for example, antimony and bismuth, the heavier members of the group, there is evidence for the presence of an inert pair of s electrons. Because the angles between the substituents of a neutral antimony(III) or bismuth(III) compound are close to 90°, it is possible to consider that, rather than using sp hydrid orbitals, the substituents are attached via pure p orbitals, with the lone pair of electrons remaining localized in the appropriate s orbital. The concept of an inert pair of electrons has some validity and it allows rationalization of much of the chemistry of these elements in the + 3 oxidation state. It is, however, difficult to provide direct experimental evidence for the effect, but it is difficult otherwise to rationalize the almost ideal octahedral structure of [SbClg]. ... 

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