Chapter 7. Periodic Properties of the Elements Media Resources Figures and Tables in Transparency Pack: Section: Figure 7.2 Effective Nuclear Charge 7.2 Effective Nuclear Charge Figure 7.3 2s and 2p Radial Probability Functions 7.2 Effective Nuclear Charge Figure 7.4 Variations in Effective Nuclear Charge 7.2 Effective Nuclear Charge for Period 2 and Period 3 Elements Figure 7.6 Trends in Bonding Atomic Radii for 7.3 Sizes of Atoms and Ions Periods 1 through 5 Figure 7.7 Cation and Anion Size 7.3 Sizes of Atoms and Ions Table 7.2 Successive Values of Ionization Energies, 7.4 Ionization Energy I, for the Elements Sodium Through Argon (kJ/mol) Figure 7.9 Trends in First Ionization Energies of the 7.4 Ionization Energy Elements Figure 7.11 Electron Affinity in kJ/mol for Selected 7.5 Electron Affinities s- and p-Block Elements Figure 7.12 Metals, Metalloids, and Nonmetals 7.6 Metals, Nonmetals, and Metalloids Figure 7.14 Representative Oxidation States of the 7.6 Metals, Nonmetals, and Metalloids Elements Table 7.4 Some Properties of the Alkali Metals 7.7 Trends for Group 1A and 2A Metals Table 7.5 Some Properties of the Alkaline Earth 7.7 Trends for Group 1A and 2A Metals Metals Table 7.6 Some Properties of the Group 6A Elements 7.8 Trends for Selected Nonmetals Table 7.7 Some Properties of the Halogens 7.8 Trends for Selected Nonmetals Table 7.8 Some Properties of the Noble Gases 7.8 Trends for Selected Nonmetals Activities: Section: Periodic Table 7.1 Development of the Periodic Table Ionization Energies 7.4 Ionization Energy Animations: Section: Periodic Properties 7.1 Development of the Periodic Table Effective Nuclear Charge 7.2 Effective Nuclear Charge Periodic Trends: Atomic Radii 7.3 Sizes of Atoms and Ions Gain and Loss of Electrons 7.3 Sizes of Atoms and Ions Ionization Energy 7.4 Ionization Energy Periodic Trends: Ionization Energies 7.4 Ionization Energy Electron Affinity 7.5 Electron Affinities Periodic Trends: Electron Affinity 7.5 Electron Affinities Periodic Trends: Acid-Base Behavior of Oxides 7.6 Metals, Nonmetals, and Metalloids Movies: Section: Sodium and Potassium in Water 7.7 Trends for Group 1A and 2A Metals Flame Tests for Metals 7.7 Trends for Group 1A and 2A Metals Physical Properties of the Halogens 7.8 Trends for Selected Nonmetals Copyright © 2012 Pearson Education, Inc. 88 Chapter 7 Reactions with Oxygen 7.8 Trends for Selected Nonmetals 3-D Models: Section: Methanethiol (methyl mercaptan) 7.3 Sizes of Atoms and Ions Water 7.6 Metals, Nonmetals, and Metalloids Hydroxide Ion 7.6 Metals, Nonmetals, and Metalloids Square Planar Structure 7.6 Metals, Nonmetals, and Metalloids Oxygen 7.8 Trends for Selected Nonmetals Sulfur 7.8 Trends for Selected Nonmetals Chlorine 7.8 Trends for Selected Nonmetals Bromine 7.8 Trends for Selected Nonmetals Iodine 7.8 Trends for Selected Nonmetals Other Resources Further Readings: Section: Chemical and Engineering News, September 8, 7.1 Development of the Periodic Table 2003 Using the Learning Cycle to Introduce Periodicity 7.1 Development of the Periodic Table The Nuts and Bolts of Chemistry 7.1 Development of the Periodic Table Mendeleev and Moseley: The Principal 7.1 Development of the Periodic Table Discoverers of the Periodic Law Mendeleev’s Other Predictions 7.1 Development of the Periodic Table Atomic Numbers Before Moseley 7.1 Development of the Periodic Table D. I. Mendeleev and the English Chemists 7.1 Development of the Periodic Table The Evolution of the Periodic System 7.1 Development of the Periodic Table Periodic Table of Elemental Abundance 7.1 Development of the Periodic Table A Different Approach to a 3-D Periodic System 7.1 Development of the Periodic Table Including Stable Isotopes Screen Percentages Based on Slater Effective 7.2 Effective Nuclear Charge Nuclear Charge as a Versatile Tool for Teaching Periodic Trends Pictorial Analogies VI: Radial and Angular Wave 7.3 Sizes of Atoms and Ions Function Plots Using Balls from Different Sports to Model the 7.3. Sizes of Atoms and Ions Variation of Atomic Sizes Periodic Contractions Among the Elements; Or, 7.3 Sizes of Atoms and Ions On Being the Right Size Ionization Energies of Atoms and Atomic Ions 7.4 Ionization Energy Trends in Ionization Energy of Transition-Metal 7.4 Ionization Energy Elements Periodicity in the Acid-Base Behavior of Oxides 7.6 Metals, Nonmetals, and Metalloids and Hydroxides Metalloids 7.6 Metals, Nonmetals, and Metalloids A Variation on the Demonstration of the Properties 7.7 Trends for Group 1A and 2A Metals of the Alkali Metals A Little Lithium May be Just What the Doctor 7.7 Trends for Group 1A and 2A Metals Ordered The Legend of Dr. Pepper/Seven-Up 7.7 Trends for Group 1A and 2A Metals Update on Intake; Calcium Consumption Low 7.7 Trends for Group 1A and 2A Metals Copyright © 2012 Pearson Education, Inc. Periodic Properties of the Elements 89 Life, Death, and Calcium 7.7 Trends for Group 1A and 2A Metals A Second Note on the Term ‘Chalcogen’ 7.8 Trends for Selected Nonmetals Allotropes and Polymorphs 7.8 Trends for Selected Nonmetals The Origin of the Term Allotrope 7.8 Trends for Selected Nonmetals Aqueous Hydrogen Peroxide: Its Household Uses 7.8 Trends for Selected Nonmetals and Concentration Units The Chemistry of Swimming Pool Maintenance 7.8 Trends for Selected Nonmetals Live Demonstrations: Section: Halogens Compete for Electrons 7.5 Electron Affinities Acidic and Basic Properties of Oxides 7.6 Metals, Nonmetals, and Metalloids Disappearing Ink 7.6 Metals, Nonmetals, and Metalloids A Dramatic Flame Test Demonstration 7.7 Trends for Group 1A and 2A Metals Simple Flame Test Techniques Using Cotton Swabs 7.7 Trends for Group 1A and 2A Metals Producing Hydrogen Gas from Calcium Metal 7.7 Trends for Group 1A and 2A Metals Preparation and Properties of Oxygen 7.8 Trends for Selected Nonmetals Plastic Sulfur 7.8 Trends for Selected Nonmetals Copyright © 2012 Pearson Education, Inc. 90 Chapter 7 Chapter 7. Periodic Properties of the Elements Common Student Misconceptions • Students have difficulty with the concepts of shielding and effective nuclear charge. As you move to the right in a period, shielding does not increase appreciably but the nuclear charge does. Therefore, effective nuclear charge increases steadily as you move to the right along the period. • Students are confused why, within a period, atomic radii decrease with increasing atomic number. • Students often do not understand slight irregularities in periodic trends for elements in each row after each ns subshell becomes filled, and after np and (n – 1)d subshells become half-filled. • Students often have problems with the signs of electron affinities; in particular, why group 1A metals have negative (exothermic) electronegativities. • Students are often confused regarding the placement of hydrogen on the periodic table; despite its common placement in column 1A, hydrogen is a nonmetal. • Students often confuse behavior of elements in aqueous phase with periodic properties determined in gas phase (ionization energy, electron affinity) or in solid phase (ionic radius). • Students often confuse isoelectronic species with those with the same number of valence electrons. Teaching Tips • Students need to be shown how position on the periodic table and electron configurations can be used to highlight periodic properties. • Emphasize the periodic table as an organizational tool; it will help students recall chemical facts. • Students find the descriptive chemistry/group trends a bit overwhelming at first. • Live demonstrations, CD videos, and web-based animations are very helpful in stimulating student interest in the group trends. Lecture Outline 7.1 Development of the Periodic Table1,2,3,4,5,6,7,8,9,10,11,12 • The periodic table is the most significant tool that chemists use for organizing and recalling chemical facts. • Elements in the same column contain the same number of outer-shell electrons or valence electrons. • How do we organize the different elements in a meaningful way that will allow us to make predictions about undiscovered elements? 1 “Periodic Properties” Animation from Instructor’s Resource CD/DVD 2 “Periodic Table” Activity from Instructor’s Resource CD/DVD 3 September 8, 2003 issue of Chemical and Engineering News from Further Readings 4 “Using the Learning Cycle to Introduce Periodicity” from Further Readings 5 “The Nuts and Bolts of Chemistry” from Further Readings 6 “Mendeleev and Moseley: The Principal Discoverers of the Periodic Law” from Further Readings 7 “The Evolution of the Periodic System” from Further Readings 8 “Mendeleev’s Other Prediction” from Further Readings 9 “Atomic Number Before Moseley” from Further Readings 10 “D. I. Mendeleev and the English Chemists” from Further Readings 11 “Periodic Tables of Elemental Abundance” from Further Readings 12 “A Different Approach to a 3–D Periodic System Including Stable Isotopes” from Further Readings Copyright © 2012 Pearson Education, Inc. Periodic Properties of the Elements 91 • Arrange elements to reflect the trends in chemical and physical properties. • The periodic table arises from the periodic patterns in the electronic configurations of the elements. • Elements in the same column contain the same number of valence electrons. • The trends within a row or column form patterns that help us make predictions about chemical properties and reactivity. • In the first attempt Mendeleev and Meyer arranged the elements in order of increasing atomic weight. • Certain elements were missing from this scheme. • For example, in 1871 Mendeleev noted that As properly belonged underneath P and not Si, which left a missing element underneath Si. He predicted a number of properties for this element. • In 1886 Ge was discovered; the properties of Ge match Mendeleev’s predictions well.