Preview Hills Chemistry for Changing Times, 15th edition by John W. Hill, Terry W. McCreary, Rill Ann Reuter, Marilyn D. Duerst (2020)

Preview Hills Chemistry for Changing Times, 15th edition by John W. Hill, Terry W. McCreary, Rill Ann Reuter, Marilyn D. Duerst (2020) Preview Hills Chemistry for Changing Times, 15th edition by John W. Hill, Terry W. McCreary, Rill Ann Reuter, Marilyn D. Duerst (2020) Preview Hills Chemistry for Changing Times, 15th edition by John W. Hill, Terry W. McCreary, Rill Ann Reuter, Marilyn D. Duerst (2020) Preview Hills Chemistry for Changing Times, 15th edition by John W. Hill, Terry W. McCreary, Rill Ann Reuter, Marilyn D. Duerst (2020)

Untitled-3 12/01/2019 14:41 Hill’s CHEMISTRY for Changing Times This page intentionally left blank A01_THOM6233_05_SE_WALK.indd 1/13/17 6:50 PM Fifteenth Edition Hill’s CHEMISTRY for Changing Times JOHN W HILL University of Wisconsin–River Falls TERRY W M c CREARY Murray State University MARILYN D DUERST University of Wisconsin–River Falls RILL ANN REUTER Winona State University Director, Physical Science Portfolio Management: Jeanne Zalesky Senior Courseware Portfolio Analyst, Physical Science: Jessica Moro Managing Producer: Kristen Flathman Content Producer: Cynthia Rae Abbott Courseware Director, Content Development: Barbara Yien Development Editor: Ed Dodd Courseware Portfolio Manager Assistant: Matthew Eva Rich Media Content Producer: Summer Giles and Nicole Constantine Director MasteringChemistry Content Development: Amir Said MasteringChemistry Senior Content Producer: Margaret Trombley MasteringChemistry Content Producer: Meaghan Fallano Production Management and Composition: 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Cataloging-in-Publication Data Names: Hill, John W (John William), author | McCreary, Terry Wade, author | Duerst, Marilyn, author | Reuter, Rill Ann, author Title: Chemistry for changing times Description: Fifteenth edition / John W Hill (University of Wisconsin-River Falls), Terry W McCreary (Murray State University); with contributions by Marilyn Duerst (University of Wisconsin-River Falls), Rill Ann Reuter (Winona State University) | Hoboken, NJ: Pearson Education, Inc., [2020] | Includes index Identifiers: LCCN 2018054352| ISBN 9780134878102 (alk paper) | ISBN 0134878108 (alk paper) Subjects: LCSH: Chemistry Textbooks Classification: LCC QD33.2 H54 2020 | DDC 540 dc23 LC record available at https://lccn.loc gov/2018054352 ISBN 10: 0-134-87810-8; ISBN 13: 978-0-134-87810-2 (Student edition) ISBN 10: 0-134-98673-3; ISBN 13: 978-0-134-98673-9 (Instructor’s Review Copy) Brief Contents Contents  vi Preface   xii To the Student  xv In Memoriam  xvi About the Authors  xviii About Our Sustainability Initiatives  xix Highlights from the 15th Edition  xxi Chemistry 1 Atoms 41 Atomic Structure 65 Chemical Bonds 97 Chemical Accounting 140 Gases, Liquids, Solids . . . and Intermolecular Forces 169 Acids and Bases 196 Oxidation and Reduction 224 Organic Chemistry 259 10 11 12 13 14 15 16 17 18 19 20 21 Polymers 303 Nuclear Chemistry 335 Chemistry of Earth 374 Air 398 Water 431 Energy 459 Biochemistry 501 Nutrition, Fitness, and Health 548 Drugs 587 Chemistry Down on the Farm . . . and in the Garden and on the Lawn  638 Household Chemicals 667 Poisons 703 Appendix: Review of Measurement and Mathematics  A-1 Glossary  G-1 Answers  Ans-1 Credits  C-1 Index  I-1 v Contents Preface  xii To the Student  xv About the Authors  xviii Chemistry 1.1 Science and Technology: The Roots of Knowledge 2 GREEN CHEMISTRY  It’s Elemental  Summary 58 • Conceptual Questions 60 •  Problems 61 • Expand Your Skills 62 •  Critical Thinking Exercises  63  •  Collaborative Group Projects  64 LET’S EXPERIMENT  Reaction in a Bag: Demonstrating the Law of Conservation of Matter  64 1.2 Science: Reproducible, Testable, Tentative, Predictive, and Explanatory  1.3 Science and Technology: Risks and Benefits  1.4 Solving Society’s Problems: Scientific Research 10 1.5 Chemistry: A Study of Matter and Its Changes 11 1.6 Classification of Matter  15 1.7 The Measurement of Matter  18 1.8 Density 24 1.9 Energy: Heat and Temperature  27 1.10 Critical Thinking  30 GREEN CHEMISTRY  Green Chemistry: Reimagining Chemistry for a Sustainable World  Summary 32 • Conceptual Questions 33 •  Problems 34 • Expand Your Skills 37 •  Critical Thinking Exercises  39  •  Collaborative Group Projects  39 LET’S EXPERIMENT  Rainbow Density Column  40 Atomic Structure 65 3.1 Electricity and the Atom  66 3.2 Serendipity in Science: X-Rays and Radioactivity 70 3.3 Three Types of Radioactivity  71 3.4 Rutherford’s Experiment: The Nuclear Model of the Atom  72 3.5 The Atomic Nucleus  74 3.6 Electron Arrangement: The Bohr Model (Orbits) 78 3.7 Electron Arrangement: The Quantum Model (Orbitals/Subshells) 83 3.8 Electron Configurations and the Periodic Table 87 GREEN CHEMISTRY  Clean Energy from Solar Fuels  Summary 91 • Conceptual Questions 92 •  Problems 93 • Expand Your Skills 94 •  Critical Thinking Exercises  95  •  Collaborative Group Projects  95 LET’S EXPERIMENT  Birthday Candle Flame Test 96 Chemical Bonds 97 4.1 The Art of Deduction: Stable Electron Configurations 98 Atoms 41 2.1 Atoms: Ideas from the Ancient Greeks  42 2.2 Scientific Laws: Conservation of Mass and Definite Proportions  44 2.3 John Dalton and the Atomic Theory of Matter  47 2.4 The Mole and Molar Mass  50 2.5 Mendeleev and the Periodic Table  54 2.6 Atoms and Molecules: Real and Relevant  57 vi 4.2 Lewis (Electron-Dot) Symbols  100 4.3 The Reaction of Sodium with Chlorine  101 4.4 Using Lewis Symbols for Ionic Compounds 104 4.5 Formulas and Names of Binary Ionic Compounds 107 4.6 Covalent Bonds: Shared Electron Pairs  110 4.7 Unequal Sharing: Polar Covalent Bonds  112 4.8 Polyatomic Molecules: Water, Ammonia, and Methane 116 Contents    vii 4.9 Polyatomic Ions  118 4.10 Guidelines for Drawing Lewis Structures  120 4.11 Molecular Shapes: The VSEPR Theory  125 4.12 Shapes and Properties: Polar and Nonpolar Molecules 129 GREEN CHEMISTRY  Green Chemistry and Chemical Bonds  Summary 133 • Conceptual Questions 134 •  Problems 135 • Expand Your Skills 137 •  Critical Thinking Exercises  138  •  Collaborative Group Projects  138 LET’S EXPERIMENT  Molecular Shapes: Please Don’t Eat the Atoms!  139 Chemical Accounting 140 5.1 Chemical Sentences: Equations  141 5.2 Volume Relationships in Chemical Equations  145 5.3 Avogadro’s Number and the Mole  147 5.4 Molar Mass: Mole-to-Mass and Mass-to-Mole Conversions 151 5.5 Solutions 156 GREEN CHEMISTRY  Atom Economy  Summary 163 • Conceptual Questions 164 •  Problems 164 • Expand Your Skills 166 •  Critical Thinking Exercises  167  •  Collaborative Group Projects  168 LET’S EXPERIMENT  Cookie Equations  168 Gases, Liquids, Solids   . . and Intermolecular Forces 169 6.1 Solids, Liquids, and Gases  170 6.2 Comparing Ionic and Molecular Substances  172 6.3 Forces between Molecules  173 6.4 Forces in Solutions  177 6.5 Gases: The Kinetic–Molecular Theory  179 6.6 The Simple Gas Laws  180 6.7 The Ideal Gas Law  186 GREEN CHEMISTRY  Supercritical Fluids  Summary 190 • Conceptual Questions 191 •  Problems 191 • Expand Your Skills 193 •  Critical Thinking Exercises  194  •  Collaborative Group Projects  194 LET’S EXPERIMENT  Blow Up My Balloon  195 Acids and Bases 196 7.1 Acids and Bases: Experimental Definitions  197 7.2 Acids, Bases, and Salts  199 7.3 Acidic and Basic Anhydrides  203 7.4 Strong and Weak Acids and Bases  205 7.5 Neutralization 207 7.6 The pH Scale  209 7.7 Buffers and Conjugate Acid–Base Pairs  212 7.8 Acids and Bases in Industry and in Daily Life 214 GREEN CHEMISTRY  Acids and Bases–Greener Alternatives  Summary 218 • Conceptual Questions 219 •  Problems 219 • Expand Your Skills 221 •  Critical Thinking Exercises   222  •  Collaborative Group Projects  222 LET’S EXPERIMENT  Acids and Bases and pH, Oh My! 223 Oxidation and Reduction 224 8.1 Oxidation and Reduction: Four Views  225 8.2 Oxidizing and Reducing Agents  232 8.3 Electrochemistry: Cells and Batteries  234 8.4 Corrosion and Explosion  240 8.5 Oxygen: An Abundant and Essential Oxidizing Agent 242 8.6 Some Common Reducing Agents  246 8.7 Oxidation, Reduction, and Living Things  248 GREEN CHEMISTRY  Green Redox Catalysis   Summary 251 • Conceptual Questions 252 •  Problems 252 • Expand Your Skills 254 •  Critical Thinking Exercises  256  •  Collaborative Group Projects  257 LET’S EXPERIMENT  Light My Fruit  258 viii   Contents 11 Nuclear Chemistry 335 Organic Chemistry 259 11.1 11.2 11.3 11.4 11.5 11.6 11.7 11.8 11.9 9.1 Organic Chemistry and Compounds  260 9.2 Aliphatic Hydrocarbons  262 9.3 Aromatic Compounds: Benzene and Its Relatives 271 9.4 Halogenated Hydrocarbons: Many Uses, Some Hazards 272 9.5 Functional and Alkyl Groups  274 9.6 Alcohols, Phenols, Ethers, and Thiols  277 9.7 Aldehydes and Ketones  283 9.8 Carboxylic Acids and Esters  286 9.9 Nitrogen-Containing Compounds: Amines and Amides 290 GREEN CHEMISTRY  The Art of Organic ­Synthesis: Green Chemists Find a Better Way  Summary 295 • Conceptual Questions 297 •  Problems 297 • Expand Your Skills 300 •  Critical Thinking Exercises  301  •  Collaborative Group Projects  301 LET’S EXPERIMENT  Saturate This!  302 GREEN CHEMISTRY  Can Nuclear Power Be Green?  Summary 367 • Conceptual Questions 368 •  Problems 369 • Expand Your Skills 371 •  Critical Thinking Exercises  371  •  Collaborative Group Projects  372 LET’S EXPERIMENT  The Brief Half-Life of Candy 373 12 Chemistry of Earth 374 12.1 Spaceship Earth: Structure and 12.2 12.3 12.4 12.5 12.6 12.7 10 Polymers 303 10.2 10.3 10.4 10.5 10.6 10.7 GREEN CHEMISTRY  Life-Cycle Impact Assessment of New Products  Summary 328 • Conceptual Questions 330 •  Problems 330 • Expand Your Skills 331 •  Critical Thinking Exercises  333  •  Collaborative Group Projects  333 LET’S EXPERIMENT  Polymer Bouncing Ball 334 Composition 375 Silicates and the Shapes of Things  377 Carbonates: Caves, Chalk, and Limestone  383 Metals and Their Ores  384 Salts and “Table Salt”  388 Gemstones and Semi-Precious Stones  389 Earth’s Dwindling Resources  390 GREEN CHEMISTRY  Critical Supply of Key Elements  10.1 Polymerization: Making Big Ones Out of Little Ones 304 Polyethylene: From the Battle of Britain to Bread Bags  305 Addition Polymerization: One +One +One + c Gives One!  309 Rubber and Other Elastomers  314 Condensation Polymers  317 Properties of Polymers  322 Plastics and the Environment  324 Natural Radioactivity  336 Nuclear Equations  339 Half-Life and Radioisotopic Dating  343 Artificial Transmutation  347 Uses of Radioisotopes  349 Penetrating Power of Radiation  353 Energy from the Nucleus  355 Nuclear Bombs  359 Uses and Consequences of Nuclear Energy  363 Summary 393 • Conceptual Questions 394 •  Problems 394 • Expand Your Skills 396 •  Critical Thinking Exercises  396  •  Collaborative Group Projects  396 LET’S EXPERIMENT  Fizzy Flintstones, Crumbling Calcium Carbonate  397 13 Air 398 13.1 Earth’s Atmosphere: Divisions and Composition 399 Chemistry of the Atmosphere  400 Pollution through the Ages  403 Automobile Emissions  407 Photochemical Smog: Making Haze While the Sun Shines  409 13.6 Acid Rain: Air Pollution ¡ Water Pollution 412 13.2 13.3 13.4 13.5 Contents    ix 13.7 The Inside Story: Indoor Air Pollution  413 13.8 Stratospheric Ozone: Earth’s Vital Shield  415 13.9 Carbon Dioxide and Climate Change  417 13.10 Who Pollutes? Who Pays?  422 GREEN CHEMISTRY  Putting Waste CO2 to Work  Summary 425 • Conceptual Questions 427 •  Problems 427 • Expand Your Skills 429 •  Critical Thinking Exercises  429  •  Collaborative Group Projects  430 15.5 Fuels and Energy: People, Horses, and Fossils 469 15.6 Coal: The Carbon Rock of Ages  472 15.7 Natural Gas and Petroleum  475 15.8 Convenient Energy  480 15.9 Nuclear Energy  481 15.10 Renewable Energy Sources  485 GREEN CHEMISTRY  Where Will We Get the Energy?  Summary 494 • Conceptual Questions 495 •  Problems 495 • Expand Your Skills 498 •  Critical Thinking Exercises  499  •  Collaborative Group Projects  499 LET’S EXPERIMENT  Let the Sun Shine  430 LET’S EXPERIMENT  Some Like It Hot and Some Like It Cool!  500 16 Biochemistry 501 14 Water 431 14.1 Water: Some Unique Properties  432 14.2 Water in Nature  436 14.3 Organic Contamination; Human and Animal 14.4 14.5 14.6 14.7 14.8 Waste 440 The World’s Water Crisis  442 Tap Water and Government Standards for Drinking Water  443 Water Consumption: Who Uses It and How Much? 445 Making Water Fit to Drink  446 Wastewater Treatment  449 16.1 Energy and the Living Cell  502 16.2 Carbohydrates: A Storehouse of Energy  504 16.3 Carbohydrates in the Diet  507 16.4 Fats and Other Lipids  510 16.5 Fats and Cholesterol  512 16.6 Proteins: Polymers of Amino Acids  516 16.7 Structure and Function of Proteins  522 16.8 Proteins in the Diet  527 16.9 Nucleic Acids: Structure and Function  528 16.10 RNA: Protein Synthesis and the Genetic Code 533 16.11 The Human Genome  535 GREEN CHEMISTRY  Green Chemistry and Biochemistry  Summary 541 • Conceptual Questions 542 •  Problems 543 • Expand Your Skills 545 •  Critical Thinking Exercises  546  •  Collaborative Group Projects  546 GREEN CHEMISTRY  Fate of Chemicals in the Water Environment  Summary  453 • Conceptual Questions  455 •  Problems  455 • Expand Your Skills 456 •  Critical Thinking Exercises   457  •  Collaborative Group Projects  457 LET’S EXPERIMENT  Disappearing Dilution  458 15 Energy 459 15.1 15.2 15.3 15.4 Our Sun, a Giant Nuclear Power Plant  460 Energy and Chemical Reactions  463 Reaction Rates  466 The Laws of Thermodynamics  467 LET’S EXPERIMENT  DNA Dessert  547 17 Nutrition, Fitness, and Health 548 17.1 17.2 17.3 17.4 17.5 17.6 17.7 17.8 Calories: Quantity and Quality  549 Minerals 552 Vitamins 555 Fiber, Electrolytes, and Water  559 Food Additives  561 Starvation, Fasting, and Malnutrition  569 Weight Loss, Diet, and Exercise  570 Fitness and Muscle  574 82    C HA P TER 3  Atomic Structure With lithium, two electrons go into the first shell, and the third must go into the second shell This process of adding electrons is continued until the second shell is filled with eight electrons, as in a neon atom, which has two of its ten electrons in the first shell and the remaining eight in the second shell A sodium atom has eleven electrons Two are in the first shell, the second shell is filled with eight electrons, and the remaining electron is in the third shell We can represent the electron configuration (or arrangement) of electrons in atoms of the first eleven elements as follows (implying that the elements between lithium and sodium are simply adding one more electron in the second shell, one by one): Element 1st shell 2nd shell H He Li  . . .   . . .   . . .  Ne Na 3rd shell Sometimes the main-shell electron configuration is abbreviated by writing the symbol for the element followed by the number of electrons in each shell, separated by commas, starting with the lowest energy level Following the color scheme from the preceding table, the main-shell configuration for sodium is simply Na 2, 8, We can continue to add electrons to the third shell until we get to argon The main-shell configuration for argon is Ar 2, 8, After argon, the notation for electron configurations is enhanced with more detail This notation is discussed in greater detail in Section 3.8 Meanwhile, Example 3.4 shows how to determine a few main-shell configurations EXAMPLE 3.4  Main-Shell Electron Configurations What is the main-shell electron configuration for fluorine? Solution Fluorine has the symbol F It has nine electrons Two of these electrons go into the first shell, and the remaining seven go into the second shell F 2, ❯ Exercise 3.4A Write the main-shell electron configurations for (a) boron and (b) aluminum These elements are in the same column of the periodic table What you notice about the number of electrons in their outermost shells? ❯ Exercise 3.4B Write the main-shell electron configurations for (a) nitrogen and (b) sulfur These elements are not in the same column of the periodic table Did you expect a similarity in the number of electrons in their outermost shells? Why or why not? 3.7  Electron Arrangement: The Quantum Model (Orbitals/Subshells)    83 SELF-ASSESSMENT Questions When electrified in a gas-discharge tube, different elements emit light that forms narrow lines that are a characteristic of each particular element b the same as those of the hydrogen spectrum c dependent on the amount of gas present in the tube d the same for all elements, but with differing intensities When an electron in an atom goes from a higher energy level to a lower one, the electron a absorbs energy b changes its volume c changes its charge d releases energy An atom in an excited state is one with an electron that has a moved to a higher energy level b been removed c bonded to another atom to make a molecule d combined with a proton to make a neutron The maximum number of electrons in the first shell of an atom is a 2 b 6 c 8 d unlimited The maximum number of electrons in the third shell of an atom is a 6 b 8 c 18 d 32 The main-shell electron configuration of magnesium is a 2, 8, 2 b 2, 8, c 2, 8, 12 d 2, 8, 8, 8, The main-shell electron configuration of sulfur is a 2, 8 b 2, 8, c 2, 8, 8, 8, 6 d 2, 8, 8, Answers: 1, a; 2, d; 3, a; 4, a; 5, c; 6, a; 7, b 3.7 Electron Arrangement: The Quantum Model (Orbitals/Subshells) Learning Objectives • Relate the idea of a quantum of energy to an orbital • Write an electron configuration (in subshell notation) for a given atom Although Bohr’s simple planetary model of the atom explained the spectrum of the hydrogen atom, it could never explain the spectra of any other elements It was eventually replaced by more sophisticated models in which electrons are treated as both particles and waves The hypothesis that the electron should have wavelike properties was first suggested in 1924 by Louis de Broglie (1892–1987), a young French physicist Although it was hard to accept because of Thomson’s evidence that electrons are particles, de Broglie’s hypothesis was experimentally verified within a few years Erwin Schrödinger (1887–1961), an Austrian physicist, used highly mathematical quantum mechanics in the 1920s to develop equations that describe the properties of electrons in atoms Fortunately, we can make use of some of Schrödinger’s results without understanding his elaborate equations The solutions to these equations express an electron’s location in terms of the probability of finding that electron in a given volume of space These variously shaped volumes of space, called orbitals, replaced the planetary orbits of the Bohr model Suppose you had a camera that could photograph electrons, and you left the shutter open while an electron zipped about the nucleus The developed picture would give a record of where the electron had been (Doing the same thing with an electric fan would give a blurred image of the rapidly moving blades, an image resembling a disk.) The electrons in the first shell would appear as a fuzzy ball (often referred to as a charge cloud or an electron cloud [Figure 3.14]) Scientists realized that each electron orbital could contain a maximum of two electrons and that some shells could contain more than one kind of orbital So, many more transitions are possible, both for absorption of energy (excitation) and release of energy (emission), than what is observed for the hydrogen atom This fact partially explains why the flame tests for elements with many more electrons than hydrogen (Figure 3.9) produce more complex line spectra (Figure 3.11) + An s orbital + A p orbital ▲ Figure 3.14  The modern charge-cloud representation of an atomic orbital is more accurate than the Bohr model (Figure 3.13) An electron cloud is the “fuzzy” region around an atomic nucleus where an electron is likely to be The type of orbital determines the general shape of the cloud The illustrations show the approximate “shape” of an s and a p orbital 84    C HA P TER   Atomic Structure High-energy laser beams can also excite electrons, and the spectra obtained can be used to identify the elements present in a given sample The modern instrumental method called laser-induced breakdown spectroscopy (LIBS) uses laser beams to identify elements in minerals or other solid samples A scanning electron microscope (SEM) with an electron-dispersive spectroscopy (EDS) attachment uses a high-energy electron beam to identify the elemental composition of the tiniest specks in samples Building Atoms by Orbital Filling Orbitals in the same shell that have the same letter designation make up a subshell (sublevel) The first shell of electrons in atoms contains a single spherical orbital called 1s, which can hold two paired electrons The second shell has two subshells, the 2s subshell and the 2p subshell The 2s subshell has just one spherical orbital and two electrons in it The 2p subshell has three dumbbell-shaped orbitals, one in each of three dimensions (Figure 3.15) Each of those 2p orbitals can contain two electrons The third shell contains nine orbitals distributed among three subshells: a spherical 3s orbital in the 3s subshell, three dumbbell-shaped 3p orbitals in the 3p subshell, and five 3d orbitals with more complicated shapes in the 3d subshell ▲ A hand-held LIBS analyzer uses laser beams to excite atoms in solid samples and analyze the resultant emissions, and can be used to identify the elements present in those samples within seconds Geologists use such instruments in the field for metal exploration s orbital p orbitals The distinctively shaped or oriented orbitals of the second energy level Combined in one drawing The orbitals centered on a single nucleus (The spherical s orbital is shown only in outline in order that the others can be seen clearly.) ▲ Figure 3.15  Electron orbitals of the second main shell In these drawings, the nucleus of the atom is located at the intersection of the axes The eight electrons that would be placed in the second shell of Bohr’s model are distributed among these four orbitals in the current model of the atom, with two electrons per orbital Electrons are in Two electrons are an s subshell in the 1s subshell 1s2 Electrons are in the first shell In building up the electron configurations of atoms of the various elements, the lower sublevels (subshells) are filled first Hydrogen has only one electron in the s orbital of the first shell The electron configuration is H 1s1 Helium has two electrons, and its electron configuration is He 1s2 Lithium has three electrons—two in the first shell and one in the second shell Because the s subshell is slightly lower in energy than the p subshell of the same shell, the third electron goes into the 2s orbital, and lithium’s electron configuration is Li 1s22s1 3.7  Electron Arrangement: The Quantum Model (Orbitals/Subshells)    85 Skipping to nitrogen, we fill the 1s and 2s subshells first The remaining electrons go into the 2p subshell, and the seven electrons are arranged as follows: N 1s22s22p3 Let’s review what this notation means: Two electrons in the first main shell Two electrons in the s subshell of the second main shell Three electrons in the p subshell of the second main shell N 1s22s22p3 First main shell Second main shell For argon, with its 18 electrons, the configuration is Ar 1s22s22p63s23p6 Note that the highest occupied subshell, 3p, is filled However, the order of subshell filling for elements with Z greater than 18 is not intuitively obvious In potassium (Z = 19), for example, the 4s subshell fills before the 3d subshell The reason for this seeming oddity is that 3d orbitals, most of which are shaped like a three-dimensional four-leafed clover (a double dumbbell), have more energy than the spherical 4s orbitals So the 4s subshell fills first Remember that we fill orbitals from the lower energy first, and then go on to the higher energy The order in which the various subshells are filled is shown in Figure 3.16 Table 3.3 gives the electron configurations for the first 20 elements The electrons in the outermost main shell, called valence electrons (Section 3.8), are shown in color So, which model should we use from now on? Which is most important? For some purposes in this text, we use only main-shell configurations of atoms to describe the distribution of electrons in atoms At other times, the electron clouds of the quantum-mechanical model are more useful Even Dalton’s model sometimes proves to be the best way to describe certain phenomena (the behavior of gases, for example) The choice of model is always based on which one is most helpful in understanding a particular concept This, after all, is the purpose of scientific models. In Chapter 4, we will see that the main-shell configurations of atoms aids in achieving a basic understanding of the two main types of chemical bonds 1s 4f 5f 3d 4d 5d 6d 2p 3p 4p 5p 6p 7p 2s 3s 4s 5s 6s 7s ▲ Figure 3.16  An order-of-filling chart for determining the electron configurations of atoms 86    C HA P TER 3  Atomic Structure TABLE 3.3  Electron Configurations for Atoms of the First 20 Elements Name Atomic Number (Z) Electron Configuration Hydrogen 1s1 Helium 1s2 Lithium 1s22s1 Beryllium 1s22s2 Boron 1s22s22p1 Carbon 1s22s22p2 Nitrogen 1s22s22p3 Oxygen 1s22s22p4 Fluorine 1s22s22p5 Neon 10 1s22s22p6 Sodium 11 1s22s22p63s1 Magnesium 12 1s22s22p63s2 Aluminum 13 1s22s22p63s23p1 Silicon 14 1s22s22p63s23p2 Phosphorus 15 1s22s22p63s23p3 Sulfur 16 1s22s22p63s23p4 Chlorine 17 1s22s22p63s23p5 Argon 18 1s22s22p63s23p6 Potassium 19 1s22s22p63s23p64s1 Calcium 20 1s22s22p63s23p64s2 EXAMPLE 3.5  Subshell Notation Without referring to Table 3.3, use subshell notation to write the electron configurations for (a) oxygen and (b) sulfur What the electron configurations of these two elements have in common? Solution a Oxygen has eight electrons We place them in subshells, starting with the lowest energy level Two go into the 1s orbital and two into the 2s orbital That leaves four electrons to be placed in the 2p subshell The electron configuration is 1s22s22p4 b Sulfur atoms have 16 electrons each The electron configuration is 1s22s22p63s23p4 Note that the total of the superscripts is 16 and that we have not exceeded the maximum capacity for any sublevel Both O and S have electron configurations with four electrons in the highest energy sublevel (outermost subshell) ❯ Exercise 3.5A Without referring to Table 3.3, use subshell notation to write out the electron configurations for (a) fluorine and (b) chlorine What the electron configurations for these two elements have in common? ❯ Exercise 3.5B Use Figure 3.16 to write the electron configurations for (a) titanium (Ti) and (b) tin (Sn) 3.8  Electron Configurations and the P ­ eriodic Table    87 SELF-ASSESSMENT Questions The shape of a 1s orbital is a circular b a dumbbell c spherical d variable The maximum number of electrons in an atomic orbital a depends on the main shell b depends on the subshell c is always two d is always eight Which of the following subshells has the highest energy? a 2p b.  2s c.  3p d.  3s What is the lowest-numbered main shell to have d orbitals? a 1 b.  2 c.  3 d.  Which of the following subshells has the lowest energy? a 4d b.  5s c.  5p d.  5d Which subshell has a total of three orbitals? a s b.  p c.  d d.  f In what main shell is a 3d subshell located? a 1 b.  3 c.  5 d.  none The electron capacity of the 4p subshell is a 3 b.  4 c.  6 d.  10 Answers: 1, c; 2, c; 3, c; 4, c; 5, b; 6, b; 7, b; 8, c 3.8 Electron Configurations and the P ­ eriodic Table Learning Objective • Describe how an element’s electron configuration relates to its location in the periodic table In general, the physical and chemical properties of elements can be correlated with their electron configurations Because the number of protons equals the number of electrons in neutral atoms, the periodic table tells us about electron configuration as well as atomic number The electron configuration is critical to understanding why and how bonding between atoms occurs, and we will explore bond formation using electron configurations in Chapter The modern periodic table (inside front cover) has horizontal rows and vertical columns ■■ ■■ Each vertical column is a group or family Elements in a group have similar chemical properties A horizontal row of the periodic table is called a period The properties of elements change in a recurring manner across a period In the United States, the groups are often indicated by a numeral followed by the letter A or B ■■ ■■ An element in an A group is a main-group element An element in a B group is a transition element IUPAC recommends numbering the groups from to 18 Both systems are indicated on the periodic table on the inside front cover, but this book uses the traditional U.S system We prefer this system because then the total number of electrons in the outermost shell of a main group element equals its column number This keeps the relationship between the electronic configuration and column number simple Family Features: Outer Electron Configurations The outermost electrons are called valence electrons They are the most important electrons in an atom; when atoms collide, it is obviously the outermost electrons of the atoms that come into closest contact with each other Those electrons are the ones involved in chemical changes and in bonding between atoms to form new compounds (Chapter 4) The period in which an element appears in the periodic table tells us how many main shells an atom of that element has Phosphorus, for example, is in the third period, so the phosphorus atom has three main shells The U.S group number for phosphorus is group 5A Thus, we can deduce that it has five valence 88    C HA P TER 3  Atomic Structure electrons Two of these are in an s orbital, and the other three are in p orbitals We can indicate the outer electron configuration of the phosphorus atom (its valence electrons) as 6  What is periodic about the periodic table? P 3s23p3 Periodic means recurring at regular intervals Figure 3.17 shows why there are periodic, or recurring, trends in the periodic table Elements in the same column have the same number of electrons in their outermost shells, and thus have similar chemical and physical characteristics The valence electrons determine most of the chemistry of an atom Because all the elements in the same group of the periodic table have the same number of valence electrons, they should have similar chemistry, and they Figure 3.17 relates the subshell configurations to the groups in the periodic table, but does not include H and He Those two elements could simply be called the 1s group On the left of Figure 3.17 is the 1s block, consisting of the first two groups For the atoms in these two groups, the last electron added goes into an s orbital, s1 and s2, respectively On the far right is the p block Its six groups correspond to the six electrons that can go into a p subshell Between these blocks are the transition metals, whose ten groups correspond to the five d orbitals in a d subshell (the d block), and the inner transition metals, where the seven f orbitals in the f subshell get filled (the f block) 1A 2A 3A 4A 5A 6A 7A s p 2p 5s 6s 7s 3B 4B 5B 6B 7B Alkaline earth metals (ns2) 4s Alkali metals (ns1) 3s 3d f 4f Inner transition metals 8B d Transition metals 1B 2B 3p 4p 4d 5p 5d 6p (ns2np1) (ns2np2) (ns2np3) (ns2np4) Halogens (ns2np5) Noble gases (ns2np6) 2s 8A 6d 5f ▲ Figure 3.17  Valence-shell electron configurations and the periodic table Family Groups Elements within a group or family have similar properties, due to similar outer electron configurations The metals in group 1A are called alkali metals, and have one valence electron ns1, where n denotes the number of the outermost main shell They react vigorously with water, producing hydrogen gas There are noticeable trends in properties within this family For example, lithium is the hardest metal in the group Sodium is softer than lithium; potassium is softer still; and so on down the group Lithium is also the least reactive toward water Sodium, potassium, rubidium, and cesium are progressively more reactive Francium is highly radioactive and extremely rare; few of its properties have been measured Hydrogen is the odd one in group 1A It is not an alkali metal but rather a typical nonmetal Based on its properties, hydrogen probably should be put in a group of its own Group 2A elements are known as alkaline earth metals The metals in this group have the outer electron configuration ns2 Most are fairly soft and moderately reactive with water Beryllium is the odd member of the group in that it is rather hard and does not react with water As in other families, there are trends in properties within the group For example, magnesium, calcium, strontium, barium, and radium are progressively more reactive toward water 3.8  Electron Configurations and the ­Periodic Table    89 Group 3A does not have a unique group name, and is referred to simply as the boron family Similarly we have the carbon family (group 4A), the nitrogen family (group 5A), and the oxygen family (group 6A), which used to be called the chalcogen family, which means “ore former.” (In Chapter 12 we will learn about a wide variety of minerals that are formed with oxygen and sulfur.) Group 7A elements are the halogens, and consist of reactive elements All have seven valence electrons with the configuration ns2np5 Halogens react vigorously with alkali metals to form crystalline solids called salts. (This is discussed further in Chapter 4.) There are trends in the halogen family as you move down the group Fluorine is most reactive toward alkali metals, chlorine is the next most reactive, and so on Fluorine and chlorine are greenish gases at room temperature, bromine is a dark reddish liquid, and iodine is a grayish/violet solid Astatine, like francium, is highly radioactive and extremely rare; few of its properties have been determined An extremely small amount of tennessine (Ts, number 117) have been created in a laboratory in Russia Members of group 8A, to the far right on the periodic table, have a complete set of valence electrons and therefore undergo few, if any, chemical reactions They are called noble gases, for their lack of chemical reactivity EXAMPLE 3.6  Valence-Shell Electron Configurations Use subshell notation to write the electron configurations for the outermost main shell of (a) strontium (Sr) and (b) arsenic (As) Solution a Strontium is in group 2A and thus has two valence electrons in an s subshell Because strontium is in the fifth period of the periodic table, its outer main shell is n = Its outer electron configuration is therefore 5s2 b Arsenic is in group 5A and the fourth period Its five outer (valence) electrons are in the n = shell, and the configuration is 4s24p3 ▲ (Upper) Lithium, an alkali metal, reacts with water to form hydrogen gas (Lower) Potassium, another alkali metal, undergoes the same reaction but much more vigorously ❯ Exercise 3.6A Use subshell notation to write the configurations for the outermost main shell of (a) cesium (Cs), (b) antimony (Sb), and (c) silicon (Si) ❯ Exercise 3.6B The valence electrons in aluminum have the configuration 3s23p1 In the periodic table, gallium is directly below aluminum, and indium is directly below gallium Use only this information to write the configurations for the valence electrons in (a) gallium and (b) indium Metals and Nonmetals Elements in the periodic table are divided into two classes by a heavy, stepped line. (See inside front cover.) Those to the left of the line are metals A metal has a characteristic luster (shininess) and generally is a good conductor of heat and electricity Except for mercury, which is a liquid, all metals are solids at room temperature Metals generally are malleable; that is, they can be hammered into thin sheets Most also are ductile, which means that they can be drawn into wires Elements to the right of the stepped line are nonmetals A nonmetal lacks metallic properties Several nonmetals are gases (e.g., oxygen, nitrogen, fluorine, and chlorine) Others are solids (e.g., carbon, sulfur, phosphorus, and iodine) Bromine is the only nonmetal that is a liquid at room temperature Some of the elements bordering the stepped line are called semimetals, or ­metalloids, and these have intermediate properties that may resemble those of both metals and nonmetals There is a lack of agreement on just which elements fit in this category ▲ (Upper) Metals such as gold are easily shaped, and they conduct heat and electricity well (Lower) Nonmetals such as sulfur are usually brittle, melt at low temperatures, and often are good insulators GREEN CHEMISTRY   Clean Energy from Solar Fuels Scott Cummings, Kenyon College Principles 1, 6, Learning Objectives • Distinguish the conversion of solar energy into electrical energy in a solar cell from the conversion of solar energy into the chemical bond energy of a solar fuel. • Explain why splitting water into the elements hydrogen and oxygen requires an energy input and why producing water by the reaction of hydrogen and oxygen releases energy Imagine a world powered by a clean fuel manufactured using sunlight and water that produces no carbon dioxide emissions when used This has been the dream of chemists around the world, who have been working for many years to develop a “solar fuel” that might someday replace some of the fossil fuels (oil, coal, and natural gas) that are so important to modern society Sunlight is a free and abundant power source The amount of solar energy reaching the Earth’s surface in one hour is as much as all of the fossil fuel energy humans use in one year The goal for chemists is to develop efficient methods to capture just a tiny part of this sunlight and convert it into a useful form Of course, the most common approach is to convert solar energy into electricity using solar panels, devices constructed from photovoltaic cells that are usually made of silicon But sunshine is intermittent, so this solar electricity is only available on sunny days A different approach is to use the energy of sunlight to promote a chemical change, converting radiant solar energy into chemical energy in the form of fuel that can be stored and used even when the sun has gone down One idea for a solar fuel is hydrogen Using sunlight to make hydrogen is one of the grand challenges of chemistry A full hydrogen energy cycle uses solar energy to split water (H2O) into hydrogen (H2) and oxygen (O2) and then uses the hydrogen as a clean fuel to produce either heat (when burned) or electricity (using a fuel cell) Splitting water requires energy input to break the chemical bonds that hold together the O and H atoms in water molecules One of the simplest ways to this is by electrolysis (Section 3.1), which requires electrical energy If the electricity is produced using a solar panel, then the hydrogen formed is a solar fuel This approach is currently expensive, and much research in chemistry is aimed at discovering new and inexpensive photovoltaic materials—including plastics—from which to construct solar panels Chemists also seek ways to make the electrodes and other components from abundant elements instead of from the precious metal platinum (Pt) For a different approach to hydrogen production, chemists are turning to green plants for inspiration Plants absorb energy from the sun and store it in the form of chemical bonds of compounds known as carbohydrates This photosynthetic reaction, which is essential to sustain life on the planet, relies on the ability of molecules in the plant to split PHOTOSYNTHESIS carbon dioxide + water + sunlight carbohydrate + oxygen ARTIFICIAL PHOTOSYNTHESIS water hydrogen + oxygen Two ways to make solar fuels Green plants use photosynthesis to produce carbohydrate fuels Chemists are trying to produce hydrogen fuel Both ­reactions use water and solar energy solar energy water (H2O) hydrogen (H2) and oxygen (O2) heat or electricity ▲ Clean energy cycle Solar energy is used to produce ­hydrogen and oxygen from water (top) Hydrogen fuel reacts with oxygen to produce water and releases energy as either heat or electricity water using sunlight Chemists are hoping to unlock the secrets of the leaf to develop “artificial photosynthesis,” which uses solar energy to produce hydrogen fuel from water Scientists at Harvard devised a system to complete the process of making liquid fuel from sunlight, carbon dioxide, and water Natural photosynthesis converts about one percent of solar energy into the carbohydrates used by plants, while the Harvard procedure turns ten percent of the energy in sunlight into fuel In natural photosynthesis, plants employ many different molecules to capture and convert solar energy Chlorophyll molecules absorb part of the solar spectrum, giving a leaf its green color To mimic this process, chemists are designing colorful synthetic dyes to capture photons from the sun When a dye absorbs light, one of its electrons is excited, which generates an excited-state molecule The challenge is to harness this excitation energy to split water before it is simply emitting as a photon (Section 3.6) Plants also employ a cluster of manganese, calcium, and oxygen atoms to crack apart water molecules and produce oxygen Chemists have been active in trying to mimic this reaction as well, using compounds made in the laboratory Solar fuels such as hydrogen embody several green chemistry principles Hydrogen fuel is only as green as the method used to make it If produced using sunlight as the energy source and water as the chemical feedstock, though, the fuel can be clean and renewable (Principle 7) Unlike fossil fuels, hydrogen is a carbon-free fuel that, if produced using sunlight, can prevent carbon dioxide emissions (Principle 1) A solar-hydrogen system relies on compounds that increase efficiency and facilitate both the water-splitting chemistry and the use of hydrogen (Principle 7) If these materials are earth-abundant and not cause harm to the environment, this process closes the clean-fuel cycle Summary    91 SELF-ASSESSMENT Questions Which pair of elements has the most similar chemical properties? a Ca and Cd b Cl and Br c P and S d Sb and Sc What is the total number of valence electrons in an atom of bromine? a 5 b.  c.  17 d.  35 Elements in the same column of the periodic table have the same a number of protons in the nucleus b total number of electrons c number of electrons in the outermost shell d number of neutrons in the nucleus Which of the following sets of elements exhibits the most ­similar chemical properties? a Ca, Zn, Kr b Pt, Au, Hg c Li, Na, K d N, O, F The valence-shell electron configuration of the halogens is a ns1 b ns2np3 c ns2np5 d ns2np6 The alkali metals are members of group a 1A b.  2A c.  3A d.  8A In the ground state, atoms of a fourth-period element must have a a 3d sublevel b electrons in the fourth shell c four valence electrons d properties similar to those of other elements in the fourth period Answers: 1, b; 2, c; 3, c; 4, a; 5, b; 6, c; 7, b Summary Section 3.1—Davy, Faraday, and others showed that matter is electrical in nature They were able to decompose compounds into elements by electrolysis or by passing electricity through molten salts Electrodes are carbon rods or metal strips that carry electricity into the electrolyte—the solution or compound that conducts electricity The electrolyte contains ions—charged atoms or groups of atoms The anode is the positive electrode, and anions (negatively charged ions) move toward it The cathode is the negative electrode, and cations (positively charged ions) move toward it Experiments with cathode rays in gas-discharge tubes showed that matter contained negatively charged particles, which were called electrons Thomson determined the mass-to-charge ratio for the electron Goldstein’s experiment showed that matter also contained positively charged particles Millikan’s oil-drop experiment measured the charge on the electron, so its mass could then be calculated Section 3.2—In his studies of cathode rays, Röntgen accidentally discovered X-rays, a highly penetrating form of radiation now used in medical diagnosis Becquerel unexpectedly discovered another type of radiation that comes from certain unstable elements Marie Curie named this new discovery radioactivity and studied it extensively Section 3.3—Radioactivity was soon classified as one of three different types Alpha (A ) particles have four times the mass of a hydrogen atom and a positive charge twice that of an electron Beta (B ) particles are energetic electrons Gamma (G) rays are a form of energy like X-rays, but are more penetrating Section 3.4—Rutherford’s experiments with alpha particles and gold foil showed that most of the alpha particles emitted toward the foil passed through it A few were deflected or, occasionally, bounced back almost directly toward the source This indicated that all the positive charge and most of the mass of an atom must be in a tiny core, which Rutherford called the nucleus Section 3.5—Rutherford called the smallest unit of positive charge the proton; it has roughly the mass of a hydrogen atom, and a charge equal in size but opposite in sign to the electron In 1932, Chadwick discovered the neutron, a nuclear particle as massive as a proton but with no charge The number of protons in an atom is the atomic number (Z) Atoms of the same element have the same number of protons but may have different numbers of neutrons; such atoms are called isotopes Different isotopes of an element are nearly identical chemically Protons and neutrons collectively are called nucleons, and the number of nucleons is called the mass number or nucleon number The difference between the mass number and the atomic number is the number of neutrons The general symbol for an isotope of element X is written A Z X, where A is the mass number and Z is the atomic number Section 3.6—Light from the sun or from an incandescent lamp produces a continuous spectrum, containing all colors Light from a gas-discharge tube produces a line spectrum, containing only certain colors Bohr explained line spectra by proposing that an electron in an atom resides only at certain discrete energy levels, which differ from one another by a quantum, or discrete unit of energy Electrons in atoms drop to a lower energy state, or ground state, after being in a higher energy state, or excited state The energy emitted when electrons move to lower energy levels manifests as a line spectrum characteristic of the particular element, with the lines corresponding to specific wavelengths (colors) of light Bohr also deduced that the energy levels of an atom could hold at most 2n2 electrons, where n is the number of the energy level, or shell A description of the shells occupied by the electrons of an atom is one way of giving the atom’s electron configuration, or arrangement of electrons Section 3.7—De Broglie hypothesized that electrons have wave properties Schrödinger developed equations that described each electron’s location in terms of an orbital—a volume of space that the electron usually occupies Each orbital holds at most two electrons Orbitals in the same shell and with the same energy make up a subshell, or sublevel, each of which is designated by a letter An s orbital is spherical and a p orbital is dumbbell-shaped The d and f orbitals have more complex shapes The first main shell can hold only one s orbital; the second can hold one s and three p orbitals; and the third can hold one s, three p, and five d orbitals In writing an electron configuration using subshell notation, we give the shell number and subshell letter, followed by a superscript indicating the number of electrons in that subshell The order of the shells and 92    C HA P TER   Atomic Structure subshells can be remembered with a chart or by looking at the periodic table Section 3.8—Elements in the periodic table are arranged vertically in groups and horizontally in periods Electrons in the outermost shell of an atom, called valence electrons, determine the reactivity of that atom Elements in a group usually have the same number of valence electrons and similarities in properties We designate groups by a number and the letter A or B The A-group elements are main-group elements The B-group elements are transition elements Group 1A elements are the alkali metals Except for hydrogen, they are all soft, low-melting, highly reactive metals Group 2A consists of the alkaline earth metals, which are fairly soft and reactive Group 7A elements, the halogens, are reactive nonmetals Group 8A elements, the noble gases, react very little or not at all A stepped line divides the periodic table into metals, which conduct electricity and heat and are shiny, malleable, and ductile, and nonmetals, which tend to lack the properties of metals Some elements bordering the stepped line, called metalloids, have properties intermediate between those of metals and nonmetals GREEN CHEMISTRY—Hydrogen is a promising clean fuel because it can be manufactured using sunlight and water and because using it does not produce carbon dioxide as waste Using a solar cell, energy from sunlight can be converted into electricity, which can then be used to split water into hydrogen and oxygen; this splitting of water can also be accomplished by a process that mimics photosynthesis The hydrogen can be burned to produce heat or used in a fuel cell to produce electricity Learning Objectives Associated Problems • Explain the electrical properties of an atom (3.1) • Describe how the properties of electricity explain the structure of atoms (3.1) • Describe the experiments that led to the discovery of X-rays and an explanation of 1, 27 • Distinguish the three main kinds of radioactivity: alpha, beta, and gamma (3.3) • Understand why atoms are believed to have a tiny nucleus surrounded by electrons (3.4) • List the particles that make up the nucleus of an atom, and give their relative masses 2, 28 • Identify elements and isotopes from their nuclear particles (3.5) • Understand how transitions of electrons in energy levels relate to absorption and 31–36 • Arrange the electrons in a given atom in energy levels (shells) (3.6) • Relate the idea of a quantum of energy to an orbital (3.7) • Write an electron configuration (in subshell notation) for a given atom (3.7) • Describe how an element’s electron configuration relates to its location in the periodic 7, 40–44 3, 27, 37, 38 radioactivity (3.2) 3, 5, 6, 19, 20 13–18 and electric charges (3.5) 10–12, 43, 44 emission (3.6) 8, 9, 30, 36 45–47, 59, 60 57, 58, 61–63 table (3.8) • Explain why splitting water into the elements hydrogen and oxygen requires an energy 64 • Distinguish the conversion of solar energy into electrical energy in a solar cell from the 65–67 input and producing water by the reaction of hydrogen and oxygen releases energy conversion of solar energy into the chemical-bond energy of a solar fuel Conceptual Questions What type of subatomic particle makes up cathode rays? What is radioactivity? How did the discovery of radioactivity contradict Dalton’s atomic theory? How was Goldstein’s experiment different from Thomson’s, and how did it reveal different information about the atom? Compare Dalton’s model of the atom with the nuclear model of the atom What were Rutherford’s two surprising conclusions, when he analyzed the results of his “gold foil” experiments? In Rutherford’s model of the atom, where are the protons, the neutrons, and the electrons found? How did Bohr’s theory change the concept of the atom? What theory uses wave properties to describe the motion of particles at the atomic and subatomic levels? Explain what is meant by the term quantum 10 Which atom absorbs more energy—one in which an electron moves from the second shell to the third shell, or an otherwise identical atom in which an electron moves from the first to the third shell? Why is this true? 11 Describe the two-step process of electron transitions that results in an emission of radiation, such as light, when an atom absorbs energy from heat, electricity, or a laser beam 12 Explain why more than one line is observed in the emission spectrum of hydrogen Problems    93 Problems Components of Atoms 30 13 How many electrons are present in a neutral atom of potassium with 19 protons in its nucleus? 31 Fill in the table 14 A neutral atom with 14 protons will have how many electrons? What element is it? 15 Use the periodic table to determine the number of protons in an atom of each of the following elements a boron b.  sulfur c.  copper 16 Use the periodic table to determine the number of protons in an atom of each of the following elements a magnesium b.  aluminum c.  zinc 17 How many electrons are there in each neutral atom of the elements listed in Question 15? 18 How many electrons are there in each neutral atom of the elements listed in Question 16? 19 Sketch a diagram of a sulfur-33 atom, with the correct number of electrons in its main shells, and the correct number of each type of nucleon 20 Sketch a diagram of a chlorine-37 atom, with the correct number of electrons in its main shells, and the correct number of each type of nucleon 21 What are the symbol, name, and atomic mass of the element with atomic number 76? You may use the periodic table 22 What are the symbol, name, and atomic number of the ­element that has 40 protons in the nuclei of its atoms? Give the symbol and name for an isotope with 30 neutrons and 25 protons Element Nickel Mass Number Number of Protons 60 108 46 Iodine 32 Number of Neutrons 74 Determine which element has 21 protons and 24 neutrons What is its mass number and number of electrons? 33 How many different elements are listed below? 23 22 11 24 25 11X 10X 5X 11X 12X 34 How many different isotopes of silver are listed below? (The X does not necessarily represent any specific element.) 108 108 110 109 107 47X 48X 47X 46X 47X 35 What is the most likely mass number of an atom with an atomic number of 14? 36 A beryllium atom has four protons, four electrons, and five neutrons What is the atom’s mass number? 37 When an atom loses three electrons, the charge on its ion is 38 When an atom gains two electrons, the charge on its ion is Nuclear Symbols and Isotopes Subshell Notation for Electron Configuration 23 The following table describes four atoms 39 Which main electron shell can be occupied by a maximum of eight electrons? Atom A Atom B Atom C Atom D Number of protons 17 18 18 17 Number of neutrons 18 17 18 17 Number of electrons 17 18 18 17 (a) Are atoms A and B isotopes? (b) Are A and C isotopes? (c) Are A and D isotopes? (d) What element is A? (e) What element is B? 24 Look at the table in Problem 23 (a) Are atoms B and C isotopes? (b) Are C and D isotopes? (c) What element is C? (d) What element is D? 25 Which atoms in Problem 23 have about the same mass? 26 Which atoms in Problem 23 have masses that are different from those of any of the others? 27 An atom with an electric charge is a an ion b a molecule c a nucleus d radioactive 28 Describe the charge and mass of the three different kinds of radioactivity 29 Give the symbol and name for an isotope with a mass number of 37 and an atomic number of 17 40 How many electrons can the third main electron shell hold? 41 Without referring to the periodic table, give the atomic numbers of the elements with the following electron ­configurations a 1s22s22p4 b 1s22s22p63s23p2 c 1s22s22p63s23p63d84s2 42 Without referring to the periodic table, give the atomic numbers of the elements with the following electron configurations a 1s22s22p5 b 1s22s22p63s23p64s1 c 1s22s22p63s23p63d104s2 43 Indicate whether each electron configuration represents an atom in the ground state or one in a possible excited state, or is incorrect In each case, explain why a 1s12s1 b 1s22s22p7 c 1s22p2 d 1s22s22p2 44 Indicate whether each electron configuration represents an atom in the ground state or one in a possible excited state, or is incorrect In each case, explain why a 1s22s23s2 b 1s22s2p23s1 c 1s22s22p62d5 d 1s22s42p2 45 Draw a grid containing 16 squares, in two rows of 8, representing the 16 elements in the periodic table from lithium 94    C HA P TER   Atomic Structure 46 to argon For each of the elements, give (a) the main-shell electron configuration and (b) the subshell notation for the electron configuration 49 Refer to the periodic table to categorize each element as a metal or a nonmetal a manganese b.  strontium c.  cesium d.  argon Write the electron configuration for the valence electrons of neutral atoms of F, Cl, and Br Explain why those atoms probably react with other atoms in similar ways 50 Using the periodic table, categorize each element as a metal, nonmetal, or semimetal a titanium b.  arsenic c.  sulfur d.  boron 47 Referring only to the periodic table, tell how the electron configurations of silicon (Si) and germanium (Ge) are similar How are they different? Use the following list of elements to answer problems 51–54 48 51 Which elements are alkali metals? Referring only to the periodic table, tell how the electron configurations of fluorine (F) and chlorine (Cl) are similar How are they different? How you expect the electron configurations of bromine (Br) and iodine (I) to be similar to those of fluorine and chlorine? Mg, Cs, Ne, P, Kr, K, Ra, N, Fe, Ca, Mo 52 Which elements are noble gases? 53 Which elements are transition metals? 54 How many of the elements are nonmetals? Expand Your Skills 55 An atom of an element has two electrons in the first shell, eight electrons in the second shell, and five electrons in the third shell From this information, give the element’s (a) atomic number, (b) name, (c) total number of electrons in each of its atoms, (d) total number of s electrons, and (e) total number of d electrons 56 Without referring to any tables in the text, color the s, p, and d blocks and mark an appropriate location for each of the following in the blank periodic table provided: (a) the fourth-period noble gas, (b) the third-period alkali metal, (c) the fourth-period halogen, and (d) a metal in the fourth period and in group 3B in its valence shell An atom of element M has at least one d electron in an unfilled shell Identify elements L and M 63 Atoms of two elements, one above the other in the same group, are in the ground state An atom of element Q has two s electrons in its outer shell and no d electrons An atom of element R has d electrons in its configuration Identify elements Q and R 64 Which of the following is true of the water-splitting ­reaction on page 88? a It produces energy, for example, electricity or heat b It requires an energy input, for example, electricity or sunlight c It produces twice as much oxygen as hydrogen d It occurs inside a fuel cell 65 What is produced when solar energy is converted into chemical-bond energy in the water-splitting reaction? a hydrogen and nitrogen b oxygen and carbon c hydrogen and oxygen d oxygen and calcium 57 Suppose that two electrons are removed from the outermost shell of a magnesium atom (a) What element’s electron configuration would the atom then have? (b) Has that atom of magnesium been changed into that element? Why or why not? 58 Suppose three electrons are added to an arsenic atom (a) Give the symbol for the element whose electron configuration matches the result (b) Has that arsenic atom been changed into that element? Why or why not? 59 Refer to Figure 3.16 and write the electron configurations of (a) iron (Fe) and (b) tin (Sn) 60 Refer to Figure 3.16 and write the electron configuration of lead (Pb) 61 Atoms of two adjacent elements in the fourth period are in the ground state An atom of element A has only s electrons in its valence shell An atom of element B has at least one p electron in its valence shell Identify elements A and B 62 Atoms of two adjacent elements in the fifth period are in the ground state An atom of element L has only s electrons 66 Which of the following is not a benefit of using a solar fuel such as hydrogen? a A solar fuel can store the energy of sunlight, which is intermittent b A solar fuel can replace some fossil fuels c Using a solar fuel such as hydrogen produces no carbon dioxide emissions d Electrodes used in electrolysis rely on platinum metal 67 Isotopes played an important role in one of the most important experiments investigating photosynthesis; the chemical reaction that converts water (H2O) and carbon dioxide (CO2) into glucose (C6H12O6) and oxygen (O2) For most of the early twentieth century, scientists thought that the oxygen produced by photosynthetic plants and algae came from carbon dioxide they absorbed To investigate this question, in the early 1940s, chemists at Stanford University used an isotope of oxygen to study the mechanism of the photosynthetic reaction The researchers fed photosynthesizing algae with water enriched with oxygen-18 and discovered that the oxygen produced was enriched with oxygen-18 Did this result support or refute the hypothesis that the O2 produced by photosynthesis comes from CO2? Collaborative Group Projects    95 Critical Thinking Exercises Apply knowledge that you have gained in this chapter and one or more of the FLaReS principles (Chapter 1) to evaluate the following ­statements or claims by heating the rock to remove some of its water.) Sometimes it does rain several days after these rain-making ceremonies 3.1 Suppose you read in the newspaper that a chemist in South America claimed to have discovered a new element with an atomic mass of 42 Extremely rare, it was found in a sample taken from the Andes Mountains Unfortunately, the chemist has used all of the sample in his analyses 3.3 Some scientists think that life on other planets might be based on silicon rather than carbon Evaluate this possibility 3.2 Some aboriginal tribes have rain-making ceremonies in which they toss pebbles of gypsum up into the air ­(Gypsum is the material used to make plaster of Paris 3.4 You come across a website selling water made from only single isotopes of hydrogen and oxygen A testimonial on the website claims that drinking only the isotopically pure water helps a person feel more refreshed throughout the day Collaborative Group Projects Prepare a PowerPoint, poster, or other presentation (as directed by your instructor) to share with the class Prepare a brief biographical report on one of the following a Humphry Davy b Antoine Henri Becquerel c Wilhelm Roentgen d Marie Curie e Robert Millikan f Niels Bohr g Alessandro Volta h Ernest Rutherford i Michael Faraday j J J Thomson Draw a grid containing 16 squares, in two rows of 8, representing the 16 elements in the periodic table from lithium to argon For each of the elements, give (a) the main-shell electron configuration and (b) the subshell notation for the electron configuration Prepare a brief report on one of the (a) alkali metals, (b) alkaline earth metals, (c) halogens, or (d) noble gases List sources and commercial uses Many different forms of the periodic table have been generated Prepare a brief report showing at least three different versions of the periodic table, and comment on their usefulness 96    C HA P TER   Atomic Structure LET’S EXPERIMENT!   Birthday Candle Flame Test Materials Needed • Colorflame birthday candles (available in party supply stores or online) • Matches or lighter • Play-Doh or an aluminum pan of sand (container big enough to stand five candles in a row) What if you could test your ability to identify and describe elements by burning a birthday candle? Would you it? Traditionally, labs creating flame-emission spectra use solutions of hazardous metal salts and Bunsen burners Even when used in tiny amounts, the metal ions in the salt solutions become volatized (airborne), creating a risk of inhalation We can reduce the hazards by using birthday candles that burn at a much lower temperature than a Bunsen burner and eliminating the preparation and disposal of solutions of metal salts Your objective will be to compare and contrast the emission spectra from the colored birthday candles Keep in mind that white light is composed of the multiple wavelengths of light that produce the whole rainbow When individual atoms are heated, they absorb energy that causes transitions from lower to higher energy states When the electrons return to the ground state, this energy is released as visible light Every element has its own unique emission spectrum that can be used as its “fingerprint” for identification To perform this experiment, gather your materials and find a room that can easily be darkened Place the five candles in the sand or Play-Doh about an inch apart, pressing them in about a quarter inch to steady them Create a small data table to record your findings The order of the candles should match that of the data table—for instance, red, purple, green, blue, orange Light the candles using a match or lighter, and darken the room to observe them better First observe the flames with your naked eye Write down the color of each flame Next, hold the diffraction film to 12 inches away from the flames and observe the dominant color for each flame Make a note about those colors Blow out the candles What did you see? How the colors seen by the naked eye compare with the emission spectra emitted by each flame? To validate your observations, check out emission-spectra ­websites such as http://webmineral.com/help/FlameTest.shtml • Diffraction grating film (available as 8.5 * 11 inch or 12 * inch sheets through online scientific education suppliers: 225 lines/mm or 500 lines/mm grating films work the best; the sheets can be cut into smaller pieces for use by multiple investigators) to identify the element in each flame Which element is in each candle? Write down your answer in the data table Light individual candles again and compare your new and old observations Are you able to justify your identifications of elements based on your observations? Why or why not? Brainstorm to find any mistake you might have made with this experiment Questions How the colors seen by the naked eye compare with the emission spectra emitted by each flame? Why did the flames produce different colors? Explain what happened within the atoms to produce the ­emission spectra Suggest potential sources of error in the analysis of the flames Justify your metal identifications based upon your observations ... Names: Hill, John W (John William), author | McCreary, Terry Wade, author | Duerst, Marilyn, author | Reuter, Rill Ann, author Title: Chemistry for changing times Description: Fifteenth edition / John. .. and honor to be a colleague of John W Hill Marilyn D Duerst My work with John Hill initially began with a review I did for an earlier edition of Chemistry for Changing Times Indeed, I did not... appreciate all your comments, corrections, and criticisms Terry W McCreary tmccreary@murraystate.edu Marilyn D Duerst marilyn. d .duerst@ uwrf.edu Rill Ann Reuter rreuter@winona.edu Preface    xv To the