Hydrogen compounds with nonmetals

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. 

In substitution reactions, hydrogen in its compounds with nonmetals often acts like a metal hence, it is listed among the metals in Table 7.1. 

Finally, we need to consider compounds containing the nonmetal hydrogen. Remember that hydrogen is an exception. In simple binary compounds with nonmetals, we treat hydrogen as a metal. As a metal in the first column, it should have a +1 charge. Thus, H2S is hydrogen sulfide. 

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). 

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. 

In its covalent compounds with nonmetals, hydrogen is assigned an oxidation state of +1. 

Hydrogen forms covalent compounds with nonmetals... 

In this case, it is best to recognize that hydrogen is always H-1 in compounds with nonmetals. Thus each H is assigned an oxidation state of -1-1, which means that the six H atoms account for a total of +6 (6 x +1). Therefore, the two carbon atoms must account for 6, and each carbon is assigned an oxidation state of —3. 

With an electronegativity only slightly above the median value of all the chemical elements, hydrogen behaves like a weakly electronegative non-metal. It forms ionic compounds with very electropositive metals and covalent compounds with nonmetals. It also forms metal hydrides with some of the transition metals. The three major hydrides it forms and with which elements are shown in Figure 10-2. 

Except for hydrogen, readily lose one electron to form ions in their compounds with nonmetals... 

In compounds with nonmetals, the oxidation number of hydrogen is +1 in compounds with metals, the oxidation number of hydrogen is —1. 

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. 

Hydrogen is unusual because it can form both a cation (1I+) and ail anion (11 ). Moreover, its intermediate electronegativity (2.2 on the Pauling scale) means that it can also form covalent bonds with all the nonmetals and metalloids. Because hydrogen forms compounds with so many elements (Table 14.2 also see Section 14.2), we shall meet more of its compounds when we study the other elements. 

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... 

Dysprosium combines with several nonmetals at high temperatures forming binary compounds with varying compositions. Heating with hydrogen produces dysprosium dihydride, DyH2, and dysprosium trihydride. DyH3. With sulfur, several sulfides have been synthesized that have the compositions... 

The metal reacts with halogens above 200°C forming its trihalides. It combines with nitrogen above 1,000°C producing a nitride, YN. It combines at elevated temperatures forming binary compounds with most nonmetals and some metalloid elements such as hydrogen, sulfur, carbon, phosphorus, silicon, and selenium. 

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. 

---