Preparation and Properties of the Elements

Phosphorus is obtained commercially from rocks bearing the phosphate minerals described earlier. In the process, crushed phosphate rock is treated with carbon and silica in an electric furnace at 1200 to 1400 °C. Under these conditions, the phosphorus is distilled out  

At temperatures below 800 °C, elemental phosphorus exists as P4 molecules having a tetrahedral structure. At the temperature used in the preparation of phosphorus, some of the molecules dissociate to P2. 

There are several allotropic forms of elemental phosphorus, the most common being the white, red, and black forms. Red phosphorus, which itself includes several forms, is obtained by heating the white form at 400 °C for several hours. An amorphous red form may also be prepared by subjecting white phosphorus to ultraviolet radiation. In the thermal transformation, several substances function as catalysts (e.g., iodine, sodium, and sulfur). Black phosphorus appears to consist of four different forms. These are obtained by the application of heat and pressure to the white form. The major uses of elemental phosphorus involve the production of phosphoric acid and other chemicals. Red phosphorus is used in making matches, and white phosphorus has had extensive use in making incendiary devices. Several of the important classes of phosphorus compounds will be discussed in later sections. 

Arsenic is usually obtained by the reduction of its oxide with carbon  

The oxide is obtained from the sulfide by roasting it in air. The stable form of arsenic is the gray or metallic form although other forms are known. Yellow arsenic is obtained by cooling the vapor rapidly, and an orthorhombic form is obtained when the vapor is condensed in the presence of mercury. Arsenic is used in the production of a variety of insecticides and herbicides, and in alloys with copper and lead. Some arsenic compounds are important medicinal compounds and a number of pigments contain arsenic compounds. The surface tension of lead is increased by dissolving a small amount of arsenic in it. This allows droplets of molten lead to assume a spherical shape, and this fact is utilized in the production of lead shot. 

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The preparation and properties of the dithiocarboxylic acids and their metal complexes have been reviewed several times.38"11 The formation of C—C bonds in the direct reaction of CS2 requires sufficiently nucleophilic carbon bases, directly or potentially accessible in the form of ambifunction-al phenoxides, organometalfic compounds, CH acidic compounds, enamines or ketimines. Carba-nions react with CS2 to give dithiocarboxylates. The preparation and purification of the adds is performed via their salts. Metal complexes are in general readily available. The bonding in these complexes is mostly of the type (27) but a bonding mode (28) is also found. Action of elemental sulfur upon heavy metal complexes of (29) aromatic dithiocarboxylic acids yields the perthio complexes (29) of these compounds. 

Preparation and properties of silicon. Elemental silicon of about 98% purity may be produced by the reduction of silicon dioxide by aluminum. 

N B —Index is airanj ed nndei headin i,s of elements placed in tlioir order of appearing m the Periodie. Classdic.ation. RoCorcmccs in italics indicate -wlicre the preparation and properties of the compound in question may be found... 

The reaction between metals and organic halides is often suitable for the synthesis of organometallic compounds of the most electropositive elements. On a laboratory scale, the derivatives of Li. Mg and Al, which are very important in synthetic work, are usually prepared in this way. Some illustrations of the method are given briefly here more detailed discussion of the preparation and properties of the compounds involved appears in Chapter 3. 

The element was first prepared by Klemm and bonner in 1937 by reducing ytterbium trichloride with potassium. Their metal was mixed, however, with KCl. Daane, Dennison, and Spedding prepared a much purer from in 1953 from which the chemical and physical properties of the element could be determined. 

Both antimony tribromide and antimony ttiiodide are prepared by reaction of the elements. Their chemistry is similar to that of SbCl in that they readily hydroly2e, form complex haUde ions, and form a wide variety of adducts with ethers, aldehydes, mercaptans, etc. They are soluble in carbon disulfide, acetone, and chloroform. There has been considerable interest in the compounds antimony bromide sulfide [14794-85-5] antimony iodide sulfide [13868-38-1] ISSb, and antimony iodide selenide [15513-79-8] with respect to their soHd-state properties, ferroelectricity, pyroelectricity, photoconduction, and dielectric polarization. 

This chapter and the following two chapters survey the properties of the elements and their compounds in relation to their locations in the periodic table. To prepare for this journey through the periodic table, we first review the trends in properties discussed in earlier chapters. We then start the journey itself with the unique element hydrogen and move on to the elements of the main groups, working from left to right across the table. The same principles apply to the elements of the d and f blocks, but these elements have some unique characteristics (mainly their wide variety of oxidation states and their ability to act as Lewis acids), and so they are treated separately in Chapter 16. 

Since the discovery of the first noble gas compound, Xe PtF (Bartlett, 1962), a number of compounds of krypton, xenon, and radon have been prepared. Xenon has been shown to have a very rich chemistry, encompassing simple fluorides, XeF2> XeF, and XeF oxides, XeO and XeO oxyf luorides, XeOF2> XeOF, and Xe02 2 perxenates perchlorates fluorosulfates and many adducts with Lewis acids and bases (Bartlett and Sladky, 1973). Krypton compounds are less stable than xenon compounds, hence only about a dozen have been prepared KrF and derivatives of KrF2> such as KrF+SbF, KrF+VF, and KrF+Ta2F11. The chemistry of radon has been studied by radioactive tracer methods, since there are no stable isotopes of this element, and it has been deduced that radon also forms a difluoride and several complex salts. In this paper, some of the methods of preparation and properties of radon compounds are described. For further information concerning the chemistry, the reader is referred to a recent review (Stein, 1983). 

In such a sequence the first complex incorporating the elements H, C, and O is a metal formyl species in Section II,A we describe the preparation and properties of such complexes. In Section II,B, stoichiometric reductions of both metal carbonyl and metal acyl species are presented and in Section II,C, homogeneous CO/H2 conversion catalysts are discussed. 

Again, the process chosen depends greatly on the physical and chemical properties of the element which it is desired to isolate. Some elements are volatile, and are more or less easily separated by distillation from the material from which they are produced some elements are attacked by water, while others resist attack some fuse at comparatively low temperatures, and can thus be separated, while others are producible in a compact state only at the enormously high temperature of the electric arc. It is necessary, therefore, to know the properties of the element required before deciding on a process for its isolation. The preparation of the remaining elements will therefore be considered from this point of view. 

Given the close similarities in preparations and properties of actinide compounds in a given oxidation state, it is convenient to discuss some general features and to follow this by additional descriptions for the separate elements. Methods of chemical... 

Progress in the preparative and structural fields of protactinium chemistry has been rapid during the past 6 years and there is now sufficient information available, particularly in the halide and oxide fields, to permit a more balanced comparison than has previously been possible with the properties of the actinide elements, on the one-hand, and those of niobium and tantalum, on the other. In this connection one must, of course, bear in mind the fact that the ionic radii of protactinium in its various valence states [Pa(V), 0.90 A and Pa(IV), 0.96 A] are appreciably larger than those of niobium or tantalum and this itself will have a considerable influence on the chemical and crystallographic properties of the elements. 

Roberts ( 1 1) surveyed the superconductive properties of the elements and recommended a critical temperature of 1.175 0.002 K for Al(cr). Since this temperature is so low, the effects of superconductivity on the thermodynamic functions are not considered. The entropy contribution due to superconductivity will be less than 0.002 J X mol . The data of Giauque and Meads (j ) and Downie and Martin (3) agree at temperatures up to 150 K but drift apart by 0.2 J X mol at 200 X and 0.17 J X mol at 300 K, with the Downie and Martin study being lower. The Takahashi (4, 5) study is even lower at 298 X. The high temperature heat capacity values are derived from the enthalpy study of Ditmars et al. (9). Their curve is intermediate between those derived from previous studies (4, 5, 6, 7, 8) and implies a flatter Cp curve near the melting point (in comparison to previous interpretations). Numerous other heat capacity and enthalpy studies are available but were omitted in this analysis. A detailed discussion of the Group IIIA metals (B, Al, and Ga) is in preparation by the JANAF staff. 

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