Periodic Properties Lecture Slides PDF

Chapter Outline (1 of 2) 8.1 Nerve Signal Transmission 8.2 The Development of the Periodic Table 8.3 Electron Configurations, Valence Electrons, and the Periodic Table 8.4 The Explanatory Power of the Quantum-Mechanical Model 8.5 Periodic Trends in the Size of Atoms and Effective Nuclear...

Chapter Outline (1 of 2) 8.1 Nerve Signal Transmission 8.2 The Development of the Periodic Table 8.3 Electron Configurations, Valence Electrons, and the Periodic Table 8.4 The Explanatory Power of the Quantum-Mechanical Model 8.5 Periodic Trends in the Size of Atoms and Effective Nuclear Charge Copyright © 2023 Pearson Canada Inc. 8-1 Chapter Outline (2 of 2) 8.6 Ionic Radii 8.7 Ionization Energy 8.8 Electron Affinities and Metallic Character 8.9 Some Examples of Periodic Chemical Behaviour, The Alkali Metals, Alkaline Earth Metals, Halogens, and Noble Gases Copyright © 2023 Pearson Canada Inc. 8-2  8.1 Nerve Signal Transmission The group 1 metals. Potassium is directly beneath sodium in the periodic table. Tiny pumps in the membranes of The basis for transmitting nerve signals in your cells are working hard to the brain and throughout the body. transport ions—especially sodium (Na+) and potassium (K+)—through ion channels in membranes the ions are pumped in opposite directions. Sodium ions are pumped out of cells, while potassium ions are pumped into cells. The result is a chemical gradient for each ion: the concentration of sodium is higher outside the cell than within, while just the opposite is true for potassium. pumped out of cells pumped into cells Copyright © 2023 Pearson Canada Inc. 8-3 Mendeleev’s Periodic Table Mendeleev’s table is based on the periodic law - states that when elements are arranged in order of increasing mass, certain properties recur periodically. Mendeleev arranged the elements in a table in which mass increased from left to right and elements with similar properties fell in the same columns. Tellurium (with higher mass) should come after iodine. Mendeleev placed tellurium before iodine and suggested that the mass of tellurium was erroneous. However, the mass was correct. Same with argon and potassium, cobalt and nickel. If the elements were organized by mass, these pairs of elements would be in reverse order. WHERE IS THE PROBLEM? Copyright © 2023 Pearson Canada Inc. 8-4 8.2 The Development of the Periodic Table The periodic table is credited primarily to the Russian chemist Dmitri Mendeleev (1834–1907), even though a similar organization had been suggested by the German chemist Julius Lothar Meyer (1830–1895). Mendeleev’s arrangement of elements in the periodic table allowed him to predict the existence of these elements, now known as gallium and germanium, and anticipate their properties. Figure 8.1 Eka-Aluminum and Eka-Silicon [gallium: Charles D. Winters/Science Source; germanium: © Richard Megna/Fundamental Photographs, NYC] Copyright © 2023 Pearson Canada Inc. 8-5 Arrangement by Atomic Numbers Moseley was doing experiments using X-ray spectroscopy, in which a sample is bombarded with a beam of electrons from a cathode ray tube. This induces the emission of X-rays from the sample, and the frequencies of the X-rays are determined using a spectrometer. Moseley found that he could arrange the frequencies of X- rays from different elements according to a sequence of whole numbers, which he named atomic numbers. Could predict the existence of three undiscovered metals— rhenium, technetium, and promethium—because these atomic numbers were missing from the sequence. Copyright © 2023 Pearson Canada Inc. 8-6 Atomic Numbers Figure 8.2 Graph Showing a Portion of Moseley’s X-Ray Data Copyright © 2023 Pearson Canada Inc. 8-7 Law vs. Theory Scientific law (e.g. periodic law) - predictive power, however, it does not explain why the properties of elements recurred, or why certain elements had similar properties. Theory - explanation of some aspect of the natural world (why), based on a body of facts that have been repeatedly confirmed through observation and experiment. Copyright © 2023 Pearson Canada Inc. 8-8 8.3 Electron Configurations, Valence Electrons, and the Periodic Table For main-group elements, the valence electrons are those in the outermost principal energy level. For transition elements, we also count the outermost d electrons among the valence electrons (even though they are not in an outermost principal energy level). Figure 8.3 Outer Electron Configurations of the First 18 Elements in the Periodic Table Copyright © 2023 Pearson Canada Inc. 8-9 Valence Electrons and Core Electrons Example. Write an electron configuration for Ge. Identify the valence electrons and core electrons. Copyright © 2023 Pearson Canada Inc. 8 - 10 Orbital Blocks in the Periodic table ns1 (the alkali metals) and ns2 (the (a) alkaline earth metals) p block, with outer electron configurations of ns2np1,ns2np2,ns2np3 (pnictogens), ns2np4 (chalcogens), ns2np5 (halogens), and (b) ns2np6 (noble gases). The transition elements compose the d block, and the lanthanoids and actinoids compose the f block. You will rarely see the 32-column periodic table (ns2,np6,nd10,nf14), Figure 8.4 The s, p, d, and f Blocks of the Periodic Table Copyright © 2023 Pearson Canada Inc. 8 - 11 Summarizing Periodic Table Organization The periodic table is divisible into four blocks corresponding to the filling of the four quantum sublevels (s, p, d, and f). The row number of main-group element is equal to the highest principal quantum number of that element. Copyright © 2023 Pearson Canada Inc. 8 - 12 Writing an Electron Configuration for an Element from Its Position in the Periodic Table Copyright © 2023 Pearson Canada Inc. 8 - 13 Noble Gases and Alkali Metals The noble gases all have eight valence electrons The alkali metals all have one valence electron. Each except for helium, which has two. They have full is one electron beyond a stable electron outer energy levels and are particularly stable and configuration, and they tend to lose that electron in unreactive. their reactions. Copyright © 2023 Pearson Canada Inc. 8 - 14  The d-Block and f-Block Elements The electron configurations of the d-block and f-block elements exhibit trends that differ somewhat from those of the main-group elements. As we move to the right across a row in the d block, the d orbitals fill as shown here: Example: Use the periodic table to write an electron configuration for selenium (Se). Copyright © 2023 Pearson Canada Inc. 8 - 15 8.4 The Explanatory Power of the Quantum-Mechanical Model 1. Write the electron configuration of a neutral atom 2. Remove/add electrons to form ions 3. What do you notice with regard to noble gases? ISOELECTRONIC Figure 8.5 Elements that Form Ions with Predictable Charges Copyright © 2023 Pearson Canada Inc. 8 - 16 Alkaline Earth Metals and Halogens The alkaline earth metals all have two valence The halogens all have seven valence electrons. Each is two electrons beyond a electrons. Each is one electron short of a stable electron configuration and they tend to stable electron configuration, and they lose those electrons in their reactions. tend to gain one electron in their reactions. Copyright © 2023 Pearson Canada Inc. 8 - 17 8.5 Periodic Trends in the Size of Atoms and Effective Nuclear Charge Non-Bonding Atomic Radius (van der Waals radius) The van der Waals radius of an atom is one-half the distance between adjacent nuclei in the atomic solid. Copyright © 2023 Pearson Canada Inc. 8 - 18 Covalent Radius A covalent radius is one-half the distance between the nuclei of two single atoms bonded together. *The bonding radii of some elements, such as helium and neon, must be approximated since they do not form either chemical bonds or metallic crystals. Covalent radii are determined from measured bond lengths. Copyright © 2023 Pearson Canada Inc. 8 - 19 Atomic Radii Generally the atomic radius - set of average covalent radii determined from measurements on a large number of elements and compounds. For example, the atomic radius of N is tabulated as 71 pm, an average of 2200 measurements. Similarly, the average atomic radius of H is 31 pm, an average of 129 measurements. Food for thought: Why do we need to take the different compounds and average them to get a reliable atomic radius? Copyright © 2023 Pearson Canada Inc. 8 - 20 Atomic Radii Trends As we move down a column (group) in the periodic table, atomic radius increases. largely determined by the valence electrons As we move to the right across a period (or As we move down a group in the row) in the periodic table, atomic radius periodic table, the highest principal decreases. quantum number (n) of the valence electrons increases. valence electrons occupy larger orbitals, resulting in larger atoms. Figure 8.7 Trends in Atomic Radius Copyright © 2023 Pearson Canada Inc. 8 - 21 Effective Nuclear Charge (1 of 3) the inward pull of the nucleus on the electrons in the outermost principal energy level (highest n value). electron in the helium ion is H 1s1 ⎯⎯⎯⎯ 1312 kJ/mol → H+ attracted to the nucleus with a 2+ He + 1s1 ⎯⎯⎯⎯ 5251 kJ/mol → He 2+ charge, the electron in the hydrogen atom is Li 1s 21s1 attracted to the nucleus by only a 1+ charge Coulombic interaction Copyright © 2023 Pearson Canada Inc. 8 - 22 Effective Nuclear Charge (2 of 3) any one electron in a multielectron atom experiences both the positive charge of the nucleus (which is attractive) and the negative charges of the other electrons (which are repulsive). Figure 8.8 Screening and Effective Nuclear Charge Copyright © 2023 Pearson Canada Inc. 8 - 23 Effective Nuclear Charge (3 of 3) Li 1s 21s1 larger Be 1s 21s 2 smaller Core electrons efficiently shield electrons in the outermost principal energy level from nuclear charge, but outermost electrons do not efficiently shield one another from nuclear charge. Copyright © 2023 Pearson Canada Inc. 8 - 24  Example On the basis of periodic trends, choose the larger atom in each pair (if possible). Explain your choices. a.N or F b.C or Ge c.N or Al d.Al or Ge Copyright © 2023 Pearson Canada Inc. 8 - 25 Summarizing Atomic Radii for Main-Group Elements: As we move down a column in the periodic table, the principal quantum number (n) of the electrons in the outermost principal energy level increases, resulting in larger orbitals and therefore larger atomic radii. As we move to the right across a row in the periodic table, the effective nuclear charge (Zeff) experienced by the electrons in the outermost principal energy level increases, resulting in a stronger attraction between the outermost electrons and the nucleus, and smaller atomic radii. Copyright © 2023 Pearson Canada Inc. 8 - 26 8.6 Ionic Radii Na [Ne]3s1 166 pm Na+ [Ne]3s0 116 pm Cations are smaller than their corresponding atoms Figure 8.10 Sizes of Atoms and Their Cations Copyright © 2023 Pearson Canada Inc. 8 - 27 Atomic and Ionic Radii (2 of 2) Cl  Ne 3s 2 3 p5 Anions are Cl−  Ne 3s 2 3 p 6 larger than their corresponding atoms isoelectronic series of ions—ions with the same number of electrons. Consider the following ions and their radii: Figure 8.11 Sizes of Atoms and Their Anions Copyright © 2023 Pearson Canada Inc. 8 - 28 Example Choose the larger atom or ion from each pair: a.S or S2− b.Ca or Ca2+ c.Br− or Kr Copyright © 2023 Pearson Canada Inc. 8 - 29 8.7 Ionization Energy the energy required to remove an electron from the atom or ion in the gaseous state. Ionization energy is always positive because removing an electron always takes energy. → Na + (g ) + e − Na(g ) ⎯⎯ IE1 = 496 kJ mol−1 Na + (g ) ⎯⎯ → Na 2+ (g ) + e − IE1 = 4560 kJ mol−1 Copyright © 2023 Pearson Canada Inc. 8 - 30 Trends in First Ionization Energy Figure 8.13 Trends in First Ionization Energy Copyright © 2023 Pearson Canada Inc. 8 - 31 Summarizing Ionization Energy for Main- Group Elements: Ionization energy generally decreases as we move down a group (or family) in the periodic table because electrons in the outermost principal level are increasingly farther away from the positively charged nucleus and are therefore held less tightly. Ionization energy generally increases as we move to the right across a period (or row) in the periodic table because electrons in the outermost principal energy level generally experience a greater effective nuclear charge (Zeff). Copyright © 2023 Pearson Canada Inc. 8 - 32 Exceptions to Trends in First Ionization Energy higher IE lower IE In oxygen electronic repulsion makes the first p electron easier to remove. Copyright © 2023 Pearson Canada Inc. 8 - 33 Trends in Second and Successive Ionization Energies (1 of 2) Na Mg [Ne] 3s1 [Ne] 3s2 Copyright © 2023 Pearson Canada Inc. 8 - 34 Trends in Second and Successive Ionization Energies (2 of 2) TABLE 8.1 Successive Values of Ionization Energies for the Elements Sodium Through Argon (kJ mol -1) Copyright © 2023 Pearson Canada Inc. 8 - 35 Example On the basis of periodic trends, choose the element with the higher first ionization energy from each pair (if possible): a.Al or S b.As or Sb c.N or Si d.O or Cl Copyright © 2023 Pearson Canada Inc. 8 - 36 8.8 Electron Affinities and Metallic Character a measure of how easily an atom will Electron Affinity accept an additional electron The energy released when an electron is added to the neutral atom in the gas phase. Cl (g ) + e − ⎯⎯ → Cl − (g ) EA1 = 349 kJ/mol Coulombic attraction between the nucleus of an atom and the incoming electron usually results in the release of energy as the electron is gained The definition makes the EA positive if a stable anion is formed. U does have a negative sign. The definition makes EA positive. Copyright © 2023 Pearson Canada Inc. 8 - 37 Electron Affinities Figure 8.15 Electron Affinities (kJ mol −1) of Selected Main-Group Elements Copyright © 2023 Pearson Canada Inc. 8 - 38 Summarizing Electron Affinity for Main- Group Elements: Most groups (columns) of the periodic table do not exhibit any definite trend in electron affinity. Among the group 1 metals, however, electron affinity decreases as we move down the column. Electron affinity generally increases as we move to the right across a period (row) in the periodic table. Copyright © 2023 Pearson Canada Inc. 8 - 39 Metallic Character Figure 8.16 Trends in Metallic Character [Na: DennisS.K/Creative Commons; Mg: Fundamental Photographs; Al: Kerrick/E+/Images; Si: Enricoros; P: Charles D. Winters/Science Source; S: Steve Gorton/DK Images; Cl: Charles D. Winters/Science Source; Bi: Ted Kinsman/Science Source; Sb: Manamana/Shutterstock; As: Harry Taylor/Dorling Kindersley, Ltd.; P: Charles D. Winters/Science Source; N: Patrizio Semproni/DK Images] Copyright © 2023 Pearson Canada Inc. 8 - 40  8.9 Some Examples of Periodic Chemical Behaviour: The Alkali Metals, the Halogens, and the Noble Gases The Alkali Metals (Group 1) readily oxidized, losing electrons to other substances Table 8.2 Properties of the Alkali Metals* Electron Atomic Radius Density at Melting Element IE1 (kJ mol−1 ) Configuration (pm) 25°C (g cm−3 ) Point (°C) Li [He] 2s1 128 520 0.535 181 Na [Ne] 3s1 166 496 0.968 102 K [Ar] 4s1 203 419 0.856 98 Rb [Kr] 5s1 220 403 1.532 39 Cs [Xe] 6s1 244 376 1.879 29 *Francium is omitted because it has no stable isotopes. 2M + X 2 → 2MX Copyright © 2023 Pearson Canada Inc. 8 - 41 Alkali Metals and Halogens 2 Na (s ) + Cl2 (g ) ⎯⎯ → 2 NaCl (s) Figure 8.17 Reaction of Sodium and Chlorine to Form Sodium Chloride [Andrew Lambert Photography/Science Source] Copyright © 2023 Pearson Canada Inc. 8 - 42 Alkali Metals and Water highly exothermic and can be explosive because the heat from the reaction can ignite the hydrogen gas 2M ( s ) + 2H 2 O ( l ) → 2M + ( aq ) + 2HO − ( aq ) + H 2 ( g ) Figure 8.18 Reactions of the Alkali Metals with Water [© Richard Megna/Fundamental Photographs, NYC] Copyright © 2023 Pearson Canada Inc. 8 - 43  The Alkaline Earth metals (Group 2) react less violently than the group 1 elements, because in group 2 elements, two electrons must be lost in order to obtain a noble gas electron configuration Table 8.3 Properties of the Alkaline Earth Metals* Electron Atomic Density at Melting Element IE1 (kJ mol−1 ) IE2 (kJ mol−1 ) Configuration Radius (pm) 25°C (g cm−3 ) Point (°C) Be [He] 2s2 96 899 1755 1.85 1287 Mg [Ne] 3s2 141 738 1450 1.74 650 Ca [Ar] 4s2 176 590 1144 1.54 842 Sr [Kr] 5s2 195 549 1063 2.64 777 Ba [Xe] 6s2 215 503 964 3.62 727 *Radium is omitted because it is radioactive. M + X 2 → MX 2 Copyright © 2023 Pearson Canada Inc. 8 - 44  The Halogens (Group 17) (1 of 2) All of the halogens are powerful oxidizing agents—they are readily reduced, gaining electrons from other substances in their reactions. Table 8.4 Properties of the Halogens* Electron Atomic Melting Point Boiling Density of Element EA (kJ mol−1 ) Configuration Radius (pm) (°C) Point (°C) Liquid (g cm−3 ) F [He] 2s2 2p5 57 328 −219 −188 1.51 Cl [Ne] 3s2 3p5 102 349 −101 −34 2.03 Br [Ar] 4s23d104p5 120 325 −7 59 3.19 I [Kr] 5s24d105p5 139 295 114 184 3.96 *Astatine is omitted because it is rare and radioactive. 2 M + n X 2 ⎯⎯ → 2 MX n 2 Fe( s ) + 3 Cl2 ( g ) ⎯⎯ → 2 FeCl3 ( s ) Copyright © 2023 Pearson Canada Inc. 8 - 45 The Halogens (Group 17) (2 of 2) 2 M + n X 2 ⎯⎯ → 2 MX n 2 Fe( s ) + 3 Cl2 ( g ) ⎯⎯ → 2 FeCl3 ( s ) H 2 ( g ) + X 2 ( g ) ⎯⎯ → 2 HX( s ) hydrogen halides Br2 ( g ) + Cl2 ( g ) ⎯⎯ → 2 BrCl( g ) react with each other to form interhalogen compounds. [© Richard Megna/Fundamental Photographs, NYC] Copyright © 2023 Pearson Canada Inc. 8 - 46  The Noble Gases (Group 18) (1 of 2) Table 8.5 Properties of the Noble Gases* Electron Atomic Density of Gas Element IE1 (kJ mol−1 ) Boiling Point (K) Configuration Radius (pm)** (g L−1 at STP) He 1s2 28 2372 4.2 0.18 Ne [He] 2s2 2p6 58 2081 27.1 0.89 Ar [Ne] 3s2 3p6 106 1521 87.3 1.76 Kr [Ar] 4s23d10 4p6 116 1351 119.9 3.69 Xe [Kr] 5s24d10 5p6 140 1170 165.1 5.78 *Radon is omitted because it is radioactive. **Since only the heavier noble gases form compounds, covalent radii for the smaller noble gases are estimated. Copyright © 2023 Pearson Canada Inc. 8 - 47 The Noble Gases (Group 18) (2 of 2) can be cryogenic liquids—liquids used to cool other substances to low temperatures Kr + F2 ⎯⎯ → KrF2 before the 1960s, no noble gas compounds were known Xe + F2 ⎯⎯ → XeF2 Xe + 2 F2 ⎯⎯ → XeF4 Xe + 3 F2 ⎯⎯ → XeF6 Copyright © 2023 Pearson Canada Inc. 8 - 48