Hydrogen Compounds of Nonmetals

Ammonia is one of the most important industrial chemicals more than ten million tons of NH3 are produced annually in the United States. You will recall (Chapter 12) that it is made by the Haber process 

Ammonia is used to make fertilizers and a host of different nitrogen compounds, notably nitric acid, HN03. 

The NH3 molecule acts as a Brensted-Lowry base in water, accepting a proton from a water molecule  

Ammonia can also act as a Lewis base when it reacts with a metal cation to form a complex ion 

Ammonia is often used to precipitate insoluble metal hydroxides such as Al(OH)3. The OH- ions formed when ammonia reacts with water precipitate the cation from solution as the hydroxide. The overall equation for the reaction is 

Ammonia, NHafg) Water, HsOf/) Hydrogen fluoride, HF(g) 

Phosphine, PHsfg) Hydrogen sulfide, H2S(g) Hydrogen chloride, HCI(g) 

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Table 21.2 lists some of the more important hydrogen compounds of the nonmetals. (Those of carbon are discussed in Chapter 22.) The physical states listed are those observed at 25°C and 1 atm. The remainder of this section is devoted to a discussion of the chemical properties of the compounds shown in boldface in die table. 

The systematic names presented for binary nonmetal-nonmetal compounds are not used for the hydrogen compounds of group III, IV, and V elements or for water. These compounds have common names which are used instead. Water and ammonia (NH, ) are the most important compounds in this class. 

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... 

Most ternary acids are hydroxyl compounds of nonmetals (oxoacids) that ionize to produce H+(aq). The formula for nitric acid is commonly written HNO3 to emphasize the presence of an acidic hydrogen atom, but it could also be written as HONO2, as its structure shows (see margin). 

The structures of the hydrogen compounds of the nonmetals are adequately described by VSEPR theory. Incorrect not all structures can be predicted by VSEPR theory, only those of electron-precise and electron-rich hydrides this theory cannot explain BiH. an electron-poor hydride. 

Some gaseous or liquid compounds of nonmetals and hydrogen ignite on contact with air and bum with a luminous flame. These are the phosphines, silanes, and boranes—the hydrides of the elements phosphorus, silicon, and boron, respectively. Of these, the luminously burning phosphines have practical importance because they can be generated by moistening of solid phosphides with plain water according to the (simplified) equations ... 

For the nonmetals, the number of valence electrons on a neutral atom is the same as the group number. Therefore, one might predict that 7A elements, such as F, would form one covalent bond to achieve an octet 6A elements, such as O, would form two covalent bonds 5 A elements, such as N, would form three covalent bonds and 4A elements, such as C, would form four covalent bonds. These predictions are borne out in many compounds. For example, consider the simple hydrogen compounds of the nonmetals of the second row of the periodic table ... 

In the first section of this chapter some of the properties of the elements hydrogen, carbon, nitrogen, phosphorus, arsenic, antimony, bismuth, oxygen, sulfur, selenium, tellurium, fluorine, chlorine, bromine, and iodine are described. The following sections are devoted to some of their compounds with one another, especially the single-bonded normal-valence compounds. Compounds of nonmetals with oxygen are discussed in the following chapter. 

Selenides. Selenium forms compounds with most elements. Biaary compounds of selenium with 58 metals and 8 nonmetals, and alloys with three other elements have been described (55). Most of the selenides can be prepared by a direct reaction. This reaction varies from very vigorous with alkah metals to sluggish and requiring high temperature with hydrogen. 

The metals are found toward the left side of the periodic table and the nonmetals are at the right side. A compound containing elements from the opposite sides of the periodic table can be expected to form a conducting solution when dissolved in water. Notice from our examples that hydrogen reacts with nonmetals to form compounds that give conducting solutions in water. In this sense, hydrogen acts like a metallic element. 

Many hydrogen compounds are acids. Acids require a different system of nomenclature than other compounds. There are two types of acids binary acids and ternary acids. All acids include the word acid in their name. Binary acids contain only two elements one of which is hydrogen and the other a nonmetal. When naming binary acids, the prefix hydro- appears before the root name of the nonmetal, and there will be an -ic suffix. As an acid, H2S would be hydrosulfuric acid. We used H2S to illustrate the fact that there can be two possible names, hydrogen sulfide or hydrosulfuric acid. If your instructor does not specify which name to use, either is correct. Technically, the name hydrosulfuric acid only applies to aqueous solutions of H2S, H2S(aq). 

Properties of hydrogen Properties of metals Band theory Properties of nonmetals Properties of transition metals Coordination compounds Crystal-held theory Complex ions... 

Hydrogen is capable of forming compounds with all elements except the noble gases. In compounds with nonmetals, hydrogen usually behaves like a metal instead of a nonmetal. Therefore, when hydrogen combines with a nonmetal, it usually has a +1 oxidation number. When hydrogen combines with a metal, it usually has a —1 oxidation number. Hydrogen compounds with the transition metals are usually nonstoichiometric. Nonstoichiometric compounds have no definite formula. 

NoH, LiAIHJ. For instance, they can act as reducing agents toward many organic compounds and are capable of hydrogenating aikynes and alkenes. Thus their H ligands are intermediate between the strictly hydridic hydrogens in the saline hydrides and the protonic hydrogens in compounds with nonmetals (e.g.. HCI, NH3). 

The important compounds of nitrogen with hydrogen are ammonia, hydrazine, and hy dr azoic acid, the parent of the shock-sensitive azides. Phosphine forms neutral solutions in water reaction of nonmetal halides with water—hydrolysis—produces oxoacids but no change in oxidation number. 

CH2=CH2 + H20 - CH3CH2OH. hydride A binary compound of a metal or metalloid with. hydrogen the term is often extended to include all binary compounds of hydrogen. A saline or saltlike hydride is a compound of hydrogen and a strongly electropositive metal a molecular hydride is a compound of hydrogen and a nonmetal a metallic hydride is a compound of certain d-block metals and hydrogen. 

In (a) a double bond is needed to make the octet of sulfur. In (b), the extra pair of electrons corresponding to the charge makes the set of atoms an ion and it eliminates the need for a double bond. In (c), that same ion is present, along with the two sodium ions to balance the charge. In (d), because hydrogen is a nonmetal, the two hydrogen atoms are covalently bonded to oxygen atoms to complete the compound. 

In its covalent compounds with nonmetals, hydrogen is assigned an oxidation state of +1. For example, in the compounds HC1, NH3, H2O, and CH4, hydrogen is assigned an oxidation state of +1. 

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