Oxidation state of lead

Pb + 40H + 2H2O [PbfOH) ] + H2t Notice, again, that the lower oxidation state of lead is formed. 

Notice, again, that the lower oxidation state of lead is formed. 

What is the composition of litharge, massicot, lead(IV) oxide, and minium Under what conditions do they form What is their structure What are the oxidation states of lead in these oxides ... 

XPS studies of the bulk oxides of lead reveal no clear evidence for the two expected oxidation states of lead in Pb304. The 4/ binding energies of lead in the rhombic and tetragonal modifications of PbO are the same within experimental error, but are greater than those for /S-PbOz. Carbon monoxide undergoes... 

Note that despite the oxidation state of lead in the reactant being +4, the ratio of moles of electrons to moles of lead(IV) oxide is 2 1 because the final product is not free lead. The number of moles of electrons involved is clearly given in the balanced equation no matter what the final product. ... 

Previous workers have not agreed on the oxidation state of lead present in manganese oxide precipitates. Cronan (23) stated that lead in manganese nodules is in the Pb state. However, Van der Weijden and Kruissink (24) have concluded from laboratory work and theoretical studies that the Pb form is more likely. 

The experiments described here provide some indirect evidence that the lead in the precipitates was at least partly in the Pb state. The lead-bearing precipitates were amorphous to x-rays. However, there was a substantial increase in the overall oxidation state of lead-bearing precipitates compared to those that did not contain lead. This is in accord with the proposed chemical model that postulates Pb. ... 

What is the oxidation state of lead in the cathode of this battery ... 

Lead has the atomic number 82 and the valence electrons are those of the 6s 6p shells. The oxidation states of lead include +2 and +4. 

Lead, like tin, forms only one hydride, plumbane. This hydride is very unstable, dissociating into lead and hydrogen with great rapidity. It has not been possible to analyse it rigorously or determine any of its physical properties, but it is probably PbH4. Although this hydride is unstable, some of its derivatives are stable thus, for example, tetraethyllead, Pb(C2Hj)4, is one of the most stable compounds with lead in a formal oxidation state of + 4. It is used as an antiknock in petrol. 

Lead forms two series of compounds corresponding to the oxidation states of +2 and +4. The +2 state is the more common. Compounds of lead(IV) are regarded as covalent, those of lead(II) as primarily ionic. Lead is amphoteric, forming plumbous (Pb(II)) and plumbic (Pb(IV)) salts as well as plumbites and plumbates, respectively. 

The interaction of species in different oxidation states can lead to higher coordinated molecules (54,116). 

The primary routes of entry for animal exposure to chromium compounds are inhalation, ingestion, and, for hexavalent compounds, skin penetration. This last route is more important in industrial exposures. Most hexavalent chromium compounds are readily absorbed, are more soluble than trivalent chromium in the pH range 5 to 7, and react with cell membranes. Although hexavalent compounds are more toxic than those of Cr(III), an overexposure to compounds of either oxidation state may lead to inflammation and irritation of the eyes, skin, and the mucous membranes associated with the respiratory and gastrointestinal tracts. Skin ulcers and perforations of nasal septa have been observed in some industrial workers after prolonged exposure to certain hexavalent chromium compounds (108—110), ie, to chromic acid mist or sodium and potassium dichromate. 

Sodium amalgam reductions of M2(CO)iq give Na+[M(CO)5] and, indeed, further reduction leads to the super reduced species [M(CO)4] in which the metals exhibit their lowest known formal oxidation state of —3. On the other hand, treatment of [M(CO)5Cl] with AICI3 and CO under pressure produces [M(CO)6]" AlCl4 from which other salts of the cation can be obtained. 

A decade after Fischer s synthesis of [(CO)5W=C(CH3)(OCH3)] the first example of another class of transition metal carbene complexes was introduced by Schrock, which subsequently have been named after him. His synthesis of [((CH3)3CCH2)3Ta=CHC(CH3)3] [11] was described above and unlike the Fischer-type carbenes it did not have a stabilizing substituent at the carbene ligand, which leads to a completely different behaviour of these complexes compared to the Fischer-type complexes. While the reactions of Fischer-type carbenes can be described as electrophilic, Schrock-type carbene complexes (or transition metal alkylidenes) show nucleophilicity. Also the oxidation state of the metal is generally different, as Schrock-type carbene complexes usually consist of a transition metal in a high oxidation state. 

Investigations of the chemical properties of plutonium have continued in many laboratories throughout the world as it has become available. This has led to the situation where the chemistry of this relative newcomer is as well understood as is that of most of the well-studied elements. The four oxidation states of plutonium—III, IV, V, and VI—lead to a chemistry which is as complex as that of any other element. It is unique among the elements in that these four oxidation states can all exist simultaneously in aqueous solution at appreciable concentration. As a metal, also, its properties are unique. Metallic plutonium has six allotropic forms, in the temperature range from room temperature to its melting point (640 C), and some of these have properties not found in any other known metal. 

Research into the aquatic chemistry of plutonium has produced information showing how this radioelement is mobilized and transported in the environment. Field studies revealed that the sorption of plutonium onto sediments is an equilibrium process which influences the concentration in natural waters. This equilibrium process is modified by the oxidation state of the soluble plutonium and by the presence of dissolved organic carbon (DOC). Higher concentrations of fallout plutonium in natural waters are associated with higher DOC. Laboratory experiments confirm the correlation. In waters low in DOC oxidized plutonium, Pu(V), is the dominant oxidation state while reduced plutonium, Pu(III+IV), is more prevalent where high concentrations of DOC exist. Laboratory and field experiments have provided some information on the possible chemical processes which lead to changes in the oxidation state of plutonium and to its complexation by natural ligands. 

It may be mentioned that the possibility of bivalence of tin in grey tin and the mercury alloy, suggested by the bipositive oxidation state of the element in many of its compounds, is ruled out because it leads to too small a value of R 1)—smaller than that for quadrivalent tin, whereas a larger value would be expected as the result of the appropriation of much of the s orbital by the unshared pair. 

The exhibition of variable valency is indeed a characteristic of transition metals. Main group metal ions such as those of groups 1 or 2 exhibit a single valence state. Other main group metals may show a number of valencies (usually two) which are related by a change in oxidation state of two units. This is typified by the occurrence of lead(iv) and lead(ii) or thallium(iii) and thallium(i). However, all the transition metals exhibit a range of valencies that is generally not limited in this manner. 

To summarize, an evaluation of the oxidation state of metals in an environment is central to determining their probable fate and biological significance. Redox reactions can lead to orders of magnitude changes in the concentration of metals in various phases, and hence in their mode and rate of transport. While equilibrium calculations are a valuable tool for understanding the direction in which changes are likely to occur, field measurements of the concentrations... 

The various oxidation states of sulfur have been determined by polarography. The electrochemical oxidation of sulfide ions in aqueous solution may lead to the production of elementary sulfur, polysulfides, sulfate, dithionate, and thiosulfate, depending on the experimental conditions. Disulfides, sulfoxides, and sulfones are typical polarographically active organic compounds. It is also found that thiols (mer-captans), thioureas, and thiobarbiturates facilitate oxidation of Hg resulting thus in anodic waves. 

The oxidation by chromic acid alone leads to a mixture of cyclobutanone and 4-hydroxybutyraldehyde the existence of an isotope effect for the oxidation of I-deuteriocyclohexanol suggests that Cr(VI) produces the ketone and lower oxidation states of chromium produce the cleavage product. 

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