Nonmetals production

Impurities in cmde metal can occur as other metals or nonmetals, either dissolved or in some occluded form. Normally, impurities are detrimental, making the metal less useful and less valuable. Sometimes, as in the case of copper, extremely small impurity concentrations, eg, arsenic, can impart a harmful effect on a given physical property, eg, electrical conductivity. On the other hand, impurities may have commercial value. For example, gold, silver, platinum, and palladium, associated with copper, each has value. In the latter situation, the purity of the metal is usually improved by some refining technique, thereby achieving some value-added and by-product credit. 

When a metal such as sodium (Na) or calcium (Ca) reacts with a nonmetal such as chlorine (Cl2), the product is ordinarily an ionic compound. The formula of that compound (e.g., NaCl, CaCl2) shows the simplest ratio between cation and anion (one Na+ ion for one Cl ion one Ca2+ ion for two Cl- ions). In that sense, the formulas of ionic compounds are simplest formulas. Notice that the symbol of the metal (Na, Ca) always appears first in the formula, followed by that of the nonmetal. 

When two nonmetals combine with each other, the product is most often a binary molecular compound. There is no simple way to deduce the formulas of such compounds. There is, however, a systematic way of naming molecular compounds that differs considerably from that used with ionic compounds. 

Chemical reaction A process in which one or more substances, called reactants, are converted to product(s), 67. See also Reaction, nonmetals, 575q, 555-558 Chernobyl nuclear accident, 525-526 Chiral center Carbon atom bonded to four different groups, 600 Chiral drugs, 601 Chloride ores, 535-536 Chlorinated water, 556 Chlorine... 

The production of steel begins when iron ore is fed into a blast furnace (Fig. 16.39). The furnace, which is approximately 40 m high, is continuously replenished from the top with a mixture of ore, coke, and limestone. Each kilogram of iron produced requires about 1.75 kg of ore, 0.75 kg of coke, and 0.25 kg of limestone. The limestone, which is primarily calcium carbonate, undergoes thermal decomposition to calcium oxide (lime) and carbon dioxide. The calcium oxide, which contains the Lewis base O2", helps to remove the acidic (nonmetal oxide) and amphoteric impurities from the ore ... 

When a free element reacts with a compound of different elements, the free element will replace one of the elements in the compound if the free element is more reactive than the element it replaces. In general, a free metal will replace the metal in the compound, or a free nonmetal will replace the nonmetal in the compound. A new compound and a new free element are produced. As usual, the formulas of the products are written on the bases presented in Chap. 5. The formula of a product does not depend on the formula of the reacting element or compound. For example, consider the reactions... 

Why are barium- and iodine-based materials selected for contrast media The production of X-ray images depends on the differences between the X-ray absorbing power of various tissues. This difference in absorbing power is called contrast and is directly dependent on tissue density. To artificially enhance the ability of a soft tissue to absorb X-rays, the density of that tissue must be increased. The absorption by targeted soft tissue of aqueous solutions of barium sulfate and iodized organic compounds provides this added density through the heavy metal barium and the heavy nonmetal iodine. 

Although the products in these equations are written as if they were simple ionic binary compounds, this is not always the case. For example, some nonmetals form clusters containing several atoms arranged in polyhedral structures. One such species is the P73- cluster, which has six phosphorus atoms at the vertices of a trigonal prism with the seventh occupying a position above a triangular face... 

As we shall see later, borides (as well as oxides, nitrides, carbides, etc.) react with water to produce a hydrogen compound of the nonmetal. Thus, the reaction of magnesium boride with water might be expected to produce BH3, borane, but instead the product is B2ff6, diborane (m.p. -165.5 °C, b.p. -92.5 °C). This interesting covalent hydride has the structure... 

When the nonmetal is in excess, the product contains the nonmetal in a lower oxidation state, as illustrated by the reactions... 

H2S, hydrogen sulfide, is the product of hydrogen gas reacting with a nonmetal, sulfur. A compound consisting of two nonmetals is primarily covalent, and has a much smaller degree of ionic character. 

The major characteristic of technetium is that it is the only element within the 29 transition metal-to-nonmetal elements that is artificially produced as a uranium-fission product in nuclear power plants. It is also the tightest (in atomic weight) of all elements with no stable isotopes. Since all of technetiums isotopes emit harmful radiation, they are stored for some time before being processed by solvent extraction and ion-exchange techniques. The two long-lived radioactive isotopes, Tc-98 and Tc-99, are relatively safe to handle in a well-equipped laboratory. 

The elements Si and Ge of group 14 act as semiconductors. A semiconductor is an element that can, to some extent, conduct electricity and heat, meaning it has the properties of both metal and nonmetals. The abihty of semiconductors to transmit variable electrical currents can be enhanced by controlling the type and amount of impurities. This is what makes them act as on-ofF circuits to control electrical impulses. This property is valuable in the electronics industry for the production of transistors, computer chips, integrated circuits, and so on. In other words, how well a semiconductor conducts electricity is not entirely dependent on the pure element itself, but also depends on the degree of its impurities and how they are controlled. 

Combination reactions occur with several nonmetals. With sulfur, it forms sulfur monobromide, S2Br2. With the addition of selenium, products are selenium monobromide, Se2Br2, and selenium tetrabromide, SeBr4. It yields unstable tellurium monobromide, Te2Br2, and a stable tetrabromide, TeBr4,with tellurium. 

Chlorine readily combines with many nonmetals. Reaction with sulfur yields sulfur dichloride, SCI2 and with phosphorus the products are phosphorus trichloride, PCI3 and phosphorus pentachloride, PCI5. 

When two (or more) metals are melted together and the melt is allowed to solidify, the product is called an alloy. (Sometimes alloys contain nonmetals such as carbon.) Since metals are more widely used as alloys than in pure condition, the nature of alloys has been the subject of much study. It has been found that some metals are miscible in all proportions, while with other pairs there is a definite limit to solubility. When a melted mixture cools, there may crystallize out (1) pure metal, (2) a solid solution, (3) a definite compound, (4) or a mixture of any of these. In the simplest case, one or the other pure metal (components) crystallizes as the temperature falls until the lowest melting point of... 

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