Oxidation of non-metallic elements

The oxides are the compounds of any element with oxygen the oxides of non-metals are defined as acidic oxides, while the oxides of metals are denoted as basic oxides. Some oxides have both acidic and basic characters and are consequently defined as amphoteric [4,77]. 

The above ideas are not limited to species with central metal ions. They apply to the higher oxidation states of non-metallic elements. Many simple anions do exist with primary hydration spheres in which the positive ends of dipoles are attracted to the central negative charge. Table 3.8 gives examples of ions that may be thought about in terms of the hydrolysis of parent hypothetical hydrated ions. 

Oxidation-reduction reactions (redox reactions) determine the chemical fate of many contaminants in groundwater and process water. Measuring the ORP (redox potential) enables us to evaluate the mobility and reactivity of non-metallic elements (sulfur, nitrogen, carbon) and metals in process water and to assess the types of redox reactions that take place in groundwater. We also use the ORP measurement as a well stabilization indicator in groundwater sampling. 

Nearly all the elements are capable of combining with oxygen to form oxides. All the oxides have a greater or less tendency to combine with water or with other oxides. In general the oxides of metals combine with water to form bases, and the oxides of non-metals combine with water to form acids. 

The three fluoro-acids HF, HS03F and CF3S03H have proved to be fruitful and essential media for preparation of many compounds of ionic species of transition metals in unusually high or low oxidation states and of cations of non-metallic elements in fractional oxidation states. 

The reactions of the dipositive lanthanide ions Sm(II), Yb(II) and Eu(II) with a number of non-metallic elements (Faraggi and Tendler 1972) and with Co(III), Ru(III) and Cr(III) complexes (Faraggi and Feder 1973, Christensen etal. 1973) have rate constants which follow the order Sm(II) > Yb(II) > Eu(II) and are independent of the oxidant electronic structure. This sequence agrees with that of the Ln"/Ln " reduction potentials, —1.55, —1.05, and — 0.35 V, respectively (Morss 1994). 

Hydroxides and oxides of non-metals behave as oxyacids or acid anhydrides and therefore react with alcohols to form esters (alkoxides of these non-metallic elements) and water ... 

In this group the outer quantum level has a full s level and two electrons in the corresponding p level. As the size of the atom increases the ionisation energy changes (see Table 8.1) and these changes are reflected in the gradual change from a typical non-metallic element, carbon, to the weakly metallic element, lead. Hence the oxides of carbon and silicon are acidic whilst those of tin and lead are amphoteric. 

Nitrogen is unusual in forming so many oxides. The acidity of the Group V oxides falls from phosphorus, whose oxides are acidic, through arsenic and antimony whose oxides are amphoteric, to the basic oxide ofbismuth. This change is in accordance with the change from the non-metallic element, phosphorus, to the essentially metallic element, bismuth. The +5 oxides are found, in each case, to be more acidic than the corresponding + 3 oxides. 

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