A Molecular Approach, 4e - Notes for Chapter (23).doc

Chapter 23. Chemistry of the Nonmetals Chapter 23. Chemistry of the Nonmetals Chapter 23. Chemistry of the Nonmetals Student Objectives 23.1 Insulated Nanowires Know that carbon forms nanotubes and that boron nitride, a material that is isoelectronic with carbon, also forms nanotubes. Know that carbon nanotubes are electrical conductors, while boron nitride nanotubes are electrical insulators. 23.2 The Main-Group Elements: Bonding and Properties Recall the periodic trends for radius, the general properties of metals and nonmetals, and the major divisions of the periodic chart. 23.3 Silicates: The Most Abundant Matter in Earth’s Crust Know that silicon and oxygen together constitute the majority of the earth’s crust. Define silicate. Know that quartz and glass have the empirical formula SiO2 but consists of tetrahedral SiO4 structural units. Know that aluminosilicates form with Al atoms in Si sites, giving the formula unit AlO2?. Know some general characteristics of the different silicate structures. Predict the structure of a given silicate. 23.4 Boron and Its Remarkable Structures Know that the different allotropes of elemental boron, B12, are based on an icosahedral structure. Know that boron reacts with halogens to form trihalides. Know that boron reacts with oxygen to form network covalent solids. Define and describe the different borane structures: closo, nido, and arachno. 23.5 Carbon, Carbides, and Carbonates Know that coal is an amorphous form of carbon that forms under pressure from the decomposition of ancient organic material and consists of three main types: lignite, bituminous, and anthracite. Know some general characteristics of coke, charcoal, activated carbon, soot, and carbon black. Know that carbon forms ionic carbides, covalent carbides, and metallic carbides when combined with different elements. Know that carbon combines with oxygen to form carbon dioxide and carbon monoxide. Know that carbon dioxide and water combine to form the carbonates: carbonic acid, bicarbonate, and carbonate. 23.6 Nitrogen and Phosphorus: Essential Elements for Life Recall that elemental nitrogen is a diatomic gas that comprises 78% of Earth’s atmosphere. Know some general characteristics of the main allotropes of phosphorus: white phosphorus, red phosphorus, and black phosphorus. Know the common nitrogen hydrides: ammonia, hydrazine, and hydrogen azide. Know the common nitrogen oxides: nitrogen oxide, nitrogen dioxide, dinitrogen trioxide, nitrous oxide, and dinitrogen tetraoxide. Know the oxyanions and oxyacids of nitrogen: nitrate, nitric acid, and nitrite. Know that phosphorus forms phosphine (PH3) and the phosphine halides PX3 and PX5. Know that phosphorus reacts with oxygen to form P4O6 and P4O10. Know that phosphoric acid and the phosphates are among the most important and useful phosphorus compounds. 23.7 Oxygen Recall that most elemental oxygen is a diatomic gas that comprises 21% of Earth’s atmosphere. Know the three oxide types: oxide, peroxide, and superoxide. Know some general characteristics of another common allotrope of oxygen, ozone (O3). 23.8 Sulfur: A Dangerous but Useful Element Know that elemental sulfur is found in a few natural deposits believed to have been formed by anaerobic bacteria and is extracted by the Frasch process. Know some general characteristics of dihydrogen sulfide. Assign oxidation states to sulfur in redox reactions. Know that sulfur dioxide forms naturally from volcanic activity and forms as a pollutant from coal and oil combustion as well as metal extraction. Know that sulfuric acid is the most abundantly produced chemical in the world. Know some general uses of sulfuric acid. 23.9 Halogens: Reactive Elements with High Electronegativity Determine the oxidation states of halogens in redox reactions. Know that halogens are not found in their elemental forms because of their high electronegativities. Know some general characteristics of fluorine, hydrofluoric acid, and chlorine. Know some general characteristics of interhalogen compounds and halogen oxides. Section Summaries Lecture Outline Terms, Concepts, Relationships, Skills Figures, Tables, and Solved Examples Teaching Tips Suggestions and Examples Misconceptions and Pitfalls Lecture Outline Terms, Concepts, Relationships, Skills Figures, Tables, and Solved Examples 23.1 Insulated Nanowires Carbon nanotubes structure electrical conductivity Boron nitride nanotubes structure electrical insulation Intro figure: illustration of carbon nanotubes Table 23.1 Properties of BN and C Figure 23.1 Boron Nitride Nanotube 23.2 The Main-Group Elements: Bonding and Properties Atomic radius Electronegativity Metals, nonmetals, metalloids unnumbered figures: periodic tables 23.3 Silicates: The Most Abundant Matter in Earth’s Crust Quartz and glass formula unit: SiO2 structure and shape: SiO4 tetrahedra Aluminosilicates AlO2 in place of SiO2 Silicate units, chains, sheets orthosilicate: SiO44? pyrosilicate: Si2O76? pyroxene repeating unit: Si2O64? formula unit: SiO32? amphibole repeating and formula unit: Si4O116? phyllosilicate repeating unit: Si4O104? formula unit: Si2O52? Predicting structures Figure 23.2 Major Elements in Earth’s Crust Figure 23.3 SiO4 Tetrahedron Figure 23.4 Structure of Quartz Example 23.1 Determining the Composition of an Aluminosilicate Figure 23.5 Pyrosilicate Structure Figure 23.6 Pyroxene Structure Figure 23.7 Amphibole Structure unnumbered figure: photo of asbestos fibers unnumbered figure: photo of mica sheets Figure 23.8 Phyllosilicate Structure Table 23.2 Types of Silicate Structures Example 23.2 Composition and Charge Balance of Silicates Examples 23.3 and 23.4 Predicting Silicate Structures Teaching Tips Suggestions and Examples Misconceptions and Pitfalls 23.1 Insulated Nanowires Nanotubes are modern examples of the descriptive chemistry of carbon, boron, and nitrogen. The microscopic structures are nearly the same, but the macroscopic properties (e.g., electrical conductivity) are different. 23.2 The Main-Group Elements: Bonding and Properties Review the periodic properties of the p-block elements: electron configurations, electronegativity, radius, electron affinity, and metallic character. 23.3 Silicates: The Most Abundant Matter in Earth’s Crust The silicates form a variety of structures, though most of them are based on a tetrahedral shape. This recognizable green pyramid is shown in all of the ball-and-stick models. Silicates, like SiO2, do not exist as discrete molecules but instead are network covalent solids. Lecture Outline Terms, Concepts, Relationships, Skills Figures, Tables, and Solved Examples 23.4 Boron and Its Remarkable Structures Elemental boron: B12 icosahedron Boron halides, BX3 Boron oxygen compounds trigonal BO3 in hexagonal shapes Boron hydrides closo-boranes nido-boranes arachno-boranes Figure 23.9 B12 Icosahedron Figure 23.10 B2O3 Structure Figure 23.11 closo-Borane Structures Figure 23.12 nido- and arachno-Boranes 23.5 Carbon, Carbides, and Carbonates Other types: coke, charcoal, activated carbon, soot, carbon black Specialized structures: fullerenes, nanotubes Carbides ionic covalent metallic Carbon oxides carbon dioxide carbon monoxide Carbonates carbonic acid washing soda baking soda baking powder Table 23.3 Approximate Composition of the Main Types of Coal unnumbered figure: photo of tires Figure 23.13 Calcium Carbide Structure unnumbered figure: micrograph of steel unnumbered figure: photo of Alka-Seltzer tablets in water Teaching Tips Suggestions and Examples Misconceptions and Pitfalls 23.4 Boron and Its Remarkable Structures Boron predominantly forms trigonal structures for boron halide and boron oxide compounds but cage structures for hydride compounds. 23.5 Carbon, Carbides, and Carbonates The crystalline allotropes of carbon are well known; other forms of carbon (e.g., coal, charcoal) are widely used. The newer forms, fullerenes and nanotubes, have been discovered and developed in the last quarter century. Conceptual Connection 23.1 Phase Changes and Pressure The carbides, particularly the covalent and metallic carbides, are important commercially because of their hardness. Carbide tips are added to saw blades made of steel to make them sharper and cut longer. The combustion products of carbon, CO2 and CO, are well known and highly relevant to daily life. Conceptual Connection 23.2 Carbonate Solubility Students always are fascinated by the fullerenes and carbon nanotubes. Graphite has a high melting point because of the strong bonds within the sheets, but it is slippery because of the weak interactions between graphite sheets. Large amounts of carbon are sequestered in ocean water, in shells of marine organisms, and in rocks. Fullerenes, particularly C60 and C70, are naturally occurring. Lecture Outline Terms, Concepts, Relationships, Skills Figures, Tables, and Solved Examples 23.6 Nitrogen and Phosphorus: Essential Elements for Life Elemental forms nitrogen: N2 (g), 78% of Earth’s atmosphere phosphorus white: P4 tetrahedra red: P4 chains black: layered like graphite Nitrogen compounds hydrides: ammonia, hydrazine, hydrogen azide oxides: nitrogen monoxide, nitrogen dioxide, dinitrogen trioxide, dinitrogen tetraxoxide, nitrous oxide nitric acid, nitrate, nitrite Phosphorus compounds hydride: phosphine halides: PX3, PX5, POX3 oxides: P4O6, P4O10 phosphoric acid, phosphates Figure 23.14 White Phosphorus Figure 23.15 Red Phosphorus Table 23.4 Oxidation States of Various Nitrogen Compounds Figure 23.16 Hydrazine and Hydrogen Peroxide Figure 23.17 Tetraphosphorus Hexaoxide and Decaoxide, P4O6 and P4O10 Table 23.5 Uses of Phosphates in the Food Industry 23.7 Oxygen Elemental oxygen O2 ozone, O3 Oxide types oxide: O2 peroxide: O22 superoxide: O2 Ozone strong oxidizing agent disinfectant ozone layer unnumbered figure: photo of ocean vents Table 23.6 Types of Oxides Teaching Tips Suggestions and Examples Misconceptions and Pitfalls 23.6 Nitrogen and Phosphorus: Essential Elements for Life A large amount of nitrogen occurs as the elemental gas N2 in the atmosphere. The nitrogen oxides also are gases. The most common ions containing nitrogen are nitrate and nitrite. Nitric acid is a strong mineral acid used commercially in the fertilizer industry. Ammonia is also a gas. Its natural supply comes from bacteria that are capable of “fixing” nitrogen: cleaving the triple bond in N2. The allotropes of elemental phosphorus include the P4 tetrahedron of white phosphorus, the chain forming interconnecting tetrahedra in red phosphorus, and the graphite-like structure of black phosphorus. Phosphoric acid is used to remove scale (i.e., rust) in the steel industry, in the production of fertilizers, and as a flavorant and preservative in soft drinks. Phosphates are widely used in detergents and in the food industry. Both extremes of nitrogen oxidation states occur in molecules that are important as fertilizers: the 3 oxidation state of N in ammonia and the +5 oxidation state of N in nitrate. Phosphorus can form molecules with an expanded octet because of low-lying d-orbitals. 23.7 Oxygen The atmospheric component gases O2 and O3 are well known, but large quantities of the most common element in Earth’s crust are found as water and oxides of many other elements. Chemical cycles of bacterial life near some volcanic vents in the ocean are based not on oxygen but on sulfur. Ozone in the upper atmosphere and as a disinfectant is useful, but ground-level ozone is a pollutant. Lecture Outline Terms, Concepts, Relationships, Skills Figures, Tables, and Solved Examples 23.8 Sulfur: A Dangerous but Useful Element Elemental form isolation by Frasch process oxidation of recycled H2S Hydrogen sulfide toxicity, odor product of bacteria and rotting different properties from those of H2O Sulfur dioxide natural volcanic source combustion product of coal and petroleum Sulfuric acid most abundant chemical produced in the world common uses Figure 23.18 The Frasch Process Figure 23.19 Sulfur Deposits Figure 23.20 Quenching Liquid Sulfur unnumbered figure: photo of molten sulfur Example 23.5 Balancing of and Assigning Oxidation States to Sulfur Reactions Table 23.7 Common Metal Sulfides Figure 23.21 Dehydration of Sucrose 23.9 Halogens: Reactive Elements with High Electronegativity Elemental forms not naturally occurring because of high electronegativity F2 from oxidation of F? Cl2 from electrolysis Interhalogen compounds ABn for n = 1, 3, 5, 7 A = large, B = small (B = F for n = 5, 7) Halogen oxides often explosive chlorine oxides often strong oxidizing agents Table 23.8 Selected Properties of the Halogens Example 23.6 Determining the Oxidation State of Halogens in Compounds Table 23.9 Comparison of Halogen X–X Bond Energy Example 23.7 Formation of Interhalogen Compounds Examples 23.8 and 23.9 Molecular Shapes of Interhalogen Compounds Example 23.10 Identifying Changes in Oxidation States Teaching Tips Suggestions and Examples Misconceptions and Pitfalls 23.8 Sulfur: A Dangerous but Useful Element Elemental sulfur is isolated directly by the Frasch process or by oxidation of H2S that is recycled from other processes. Hydrogen sulfide is toxic, so it must be removed and/or recycled anyway. Hydrogen sulfide has the characteristic smell of rotting eggs. It can be smelled at about 20 ppb, but the sense of smell is desensitized after exposure. Sulfur dioxide is an environmental pollutant that arises from combustion of sulfur-containing coal and petroleum products. Large quantities of sulfur dioxide also are produced from volcanic activity. Hydrogen sulfide looks as if it should resemble water based on their formulas. However, nearly everything about these two compounds, including bond angle, toxicity, and physical properties, is different. 23.9 Halogens: Reactive Elements with High Electronegativity Elemental halogens can be formed by electrolysis of the halide salts. Halogen oxides are often explosive, and most of the known ones of chlorine are strong oxidizing agents. Like the Group 1A and 2A metals, none of the elemental forms of the halogens occurs naturally because of their high reactivity. Additional Problem for Predicting Silicate Structures (Examples 23.3, 23.4) Predict the silicate structure for the mineral talc Mg3Si4O10(OH)2 that serves as the basis for talcum powder, and show that the formula is charge neutral. Si to O Ratio Determine the ratio of Si to O in the formula. Si:O ratio is 4:10 or 2:5. The other two oxygens occur as hydroxides and are not part of the silicate structures. (That situation is indicated by the OH in the parentheses.) Match Ratio to List Match the Si:O ratio to the type of silicate in Table 23.2. The 2:5 ratio is indicated for phyllosilicate sheets with a formula unit of Si2O52. Anion Charge Determine the total anion charge. Si2O52: 2 @ 2 = 4 OH: 2 @ 1 = 2 total anionic charge = 6 Cation Charge Determine the total cation charge and show that it matches the total anion charge. Mg2+: 3 @ +2 = +6 total cationic charge = +6 The anionic and cationic charges balance so the formula is charge neutral. Additional Problem for Determining the Oxidation State of Halogens in Compounds (Example 23.6) Calculate the oxidation state for Cl in the compounds: a) Cl2O6 b) ClF3 c) HClO4 Solution a Oxidation states: oxygen: 3 @ 2 = 6 chlorine: 2 @ ?? = +6 Chlorine must be +3 oxidation state. Solution b Oxidation states: fluorine: 3 @ 1 = 3 chlorine: 1 @ ?? = +3 Chlorine must be +3 oxidation state. Solution c Oxidation states: hydrogen: 1 @ +1 = +1 oxygen: 4 @ 2 = 8 chlorine: 1 @ ?? = +7 Chlorine must be +7 oxidation state. 310 Copyright © 2017 by Education, Inc. 311 Copyright © 2017 by Education, Inc.