Nonmetals with hydrogen

The reactivity of hydrogen with nonmetals reflects its much greater tendency to hold on to its electron relative to the alkali metals. Unlike the alkali metals, hydrogen reacts with most nonmetals to form molecular compounds in which its electron is shared with, rather than completely transferred to, the other nonmetal. For example, we have seen that sodium metal reacts vigorously with chlorine gas to produce the ionic... 

We have seen that, particularly in the presence of water, hydrogen does readily form ions in which the hydrogen atom has lost its electron, cco (Section 4.3) For example, HC1( ) dissolves in H2O to form a solution of hydrochloric add, HCl(aq), in which the electron of the hydrogen atom is transferred to the chlorine atom—a solution of hydrochloric acid consists largely of H (aq) cuid ClT aq) ions stabilized by the H2O solvent. Indeed, the ability of molecular compoimds of hydrogen with nonmetals to form acids in water is one of the most importcuit aspects of aqueous chemistry. We will discuss the chemistry of acids and bases in detail later in the text, particularly in Chapter 16. 

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. 

The oxidation number of hydrogen is +1 in combination with nonmetals and —1 in combination with metals. 

B Aluminum forms an amphoteric oxide in which it has the oxidation state +3 therefore, aluminum is the element. 14.3B Hydrogen is a nonmetal and a diatomic gas at room temperature. It has an intermediate electronegativity (x — 2.2), so it forms covalent bonds with nonmetals and forms anions in combination with metals. In contrast, Group 1 elements are solid metals that have low electronegativities and form cations in combination with nonmetals. 

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. 

WM Metals are found to the left of the staircase, with the exception of hydrogen, and nonmetals are found to the right of the staircase. Several elements adjoining the staircase are classified as metalloids. 

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). 

On the other hand, with nonmetals, such as hydrogen, carbon, sulfur, and phosphorus, oxygen forms covalent oxides ... 

Covalent (molecules containing covalently bound hydrogen to nonmetals, with individual molecules held together by intermolecular forces, e.g., CH4, SiHa) Metallic/interstitial (hydrogen molecules are contained in vacant interstitial sites of a transition-metal lattice, e.g., PdHo.e)... 

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. 

SAFETY PROFILE A poison. Flammable by chemical reaction an oxidizer. Explosive reaction with hydrogen peroxide, chlorine + ethylene. Reacts violently with molten potassium, molten sodium, S, (H2S + BaO + air). Forms explosive mixtures with nonmetals [e.g., phosphorus (impact-sensitive), sulfur (friction-sensitive)]. Incompatible with alkali metals, reducing materials. Dangerous when heated to decomposition it emits highly toxic fumes of Hg. See also MERCURY COMPOUNDS, INORGANIC. 

Hydrogen reacts with nonmetals to form binary molecular hydrides. For example, H2 combines with the halogens to form colorless, gaseous hydrogen halides (Figure 6-5) ... 

Reaction (a) is a reaction between hydrogen and another nonmetal. The product, HI, must be molecular. Reaction (b) is the reaction of hydrogen with an active Group lA metal. Thus, KH must be ionic. The products of reaction (c) are molecular H2(g) and the strong base, NaOH, which is ionic. 

Like oxygen, sulfur gains two electrons and forms the sulfide ion (S ) when it reacts with metals or with hydrogen. But in its reactions with nonmetals, sulfur can have other oxidation numbers. Much of the sulfur produced in the United States is taken from deposits of elemental sulfur by the Frasch process, shown in Figure 8.8. 

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