Chemistry Second Edition Julia Burdge Lecture Power Points
Chemistry Second Edition Julia Burdge Lecture Power. Points Jason A. Kautz University of Nebraska-Lincoln 7 Electron Configuration and the Periodic Table Copyright (c) The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. 1
7 Electron Configuration and the Periodic Table 7. 1 Development of the Periodic Table 7. 2 The Modern Periodic Table Classification of Elements Representing Free Elements in Chemical Equations 7. 3 Effective Nuclear Charge 7. 4 Periodic Trends in Properties of Elements Atomic Radius Ionization Energy Electron Affinity Metallic Character 7. 5 Electron Configuration of Ions of Main Group Elements Ions of d-Block Elements 7. 6 Ionic Radius Comparing Ionic Radius with Atomic Radius Isoelectronic Series
7 Electron Configuration and the Periodic Table 7. 7 Periodic Trends in Chemical Properties of the Main Group Elements General Trends in Chemical Properties of the Active Metals Properties of Other Main Group Elements Comparison of Group 1 A and Group 1 B Elements Variation in Properties of Oxides Within a Period
7. 1 Development of the Periodic Table In 1864 John Newlands referred to the law of octaves. In 1869 Dmitri Mendeleev and Lothar Meyer independently proposed the idea of periodicity. Mendeleev grouped elements (66) according to properties. Mendeleev predicted properties for elements not yet discovered. Mendeleev could not explain inconsistencies.
Development of the Periodic Table In 1913 Henry Moseley discovered the correlation between the number of protons (atomic number) and frequency of X-rays generated. Entries today include atomic number and symbol; and are arranged according to electron configuration.
7. 2 The Modern Periodic Table
The Modern Periodic Table The main group elements (also called the representative elements) are the elements in Groups 1 A through 7 A.
The Modern Periodic Table The noble gases are found in Group 8 A.
The Modern Periodic Table The transition metals are found in Group 1 B and 3 B through 8 B. Group 2 B have filled d subshells and are not transition metals.
The Modern Periodic Table The lanthanides and actinides make up the f-block elements.
The Modern Periodic Table There is a distinct pattern to the electron configurations of the elements in a particular group. For Group 1 A: [noble gas]ns 1 For Group 2 A: [noble gas]ns 2
The Modern Periodic Table The outermost electrons of an atom are called the valence electrons. Valence electrons are involved in the formation of chemical bonds. Similarity of valence electron configurations help predict chemical properties. For Group 1 A: [noble gas]ns 1 core For Group 2 A: [noble gas]ns 2 core valence For Group 7 A: [noble gas]ns 2 np 5 core valence
The Modern Periodic Table Metals are always represented by their empirical formulas. Nonmetals may be written as an empirical formula (C) or as polyatomic molecules (H 2, N 2, O 2, F 2, Cl 2, Br 2, I 2, and P 4). Sulfur is usually written as S instead of S 8 elemental sulfur (S) elemental sodium (Na)
The Modern Periodic Table Noble gases all exist as isolated atoms and are represented with their elemental symbol (Xe, He, etc. ) Metalloids are represented with empirical formulas (B, Si, Ge, etc. ) Neon(Ne) Silicon (Si)
7. 3 Effective Nuclear Charge (Zeff) is the actual magnitude of positive charge that is experienced by an electron in the atom. Zeff = Z – σ Z is the nuclear charge or simply the number of protons in the nucleus. σ is the shielding constant. Zeff increases from left to right across a period; changes very little down a column Z Zeff Li Be B C N O F 3 4 5 6 7 8 9 1. 28 1. 91 2. 42 3. 14 3. 83 4. 45 5. 10
Effective Nuclear Charge (Zeff) is the actual magnitude of positive charge that is experienced by an electron in the atom. Zeff = Z – σ
7. 4 Periodic Trends in Properties of Elements Atomic radius is the distance between the nucleus of an atom and its valence shell. The metallic radius is half the distance between the nuclei of two adjacent, identical metal atoms.
Periodic Trends in Properties of Elements The covalent radius is half the distance between adjacent, identical nuclei in a molecule.
Periodic Trends in Properties of Elements The atomic radius increases from top to bottom down a group. ~increasing n Atomic radius decreases from left to right across a period. ~increasing Zeff
Periodic Trends in Properties of Elements Atomic radius decreases left to right across a period due to increased electrostatic attraction between the effective nuclear charge and the charge on the valence shell.
Periodic Trends in Properties of Elements Ionization energy (IE) is the minimum energy required to remove an electron from an atom in the gas phase. Na(g) → Na+(g) + e− IE 1(Na) = 495. 8 k. J/mol.
Periodic Trends in Properties of Elements IE 1 value for the main group elements (k. J/mol).
Periodic Trends in Properties of Elements First ionization energy as a function of atomic number.
Periodic Trends in Properties of Elements
Periodic Trends in Properties of Elements
Periodic Trends in Properties of Elements It is possible to remove additional electrons in subsequent ionizations. Na(g) → Na+(g) + e− IE 1(Na) = 496 k. J/mol. Na+(g) → Na 2+(g) + e− IE 2(Na) = 4562 k. J/mol.
Periodic Trends in Properties of Elements It takes more energy to remove the 2 nd, 3 rd, 4 th, etc. electrons and even much more energy to remove core electrons. Core electrons are closer to nucleus Core electrons experience greater Zeff
Periodic Trends in Properties of Elements Electron Affinity (EA) is the energy released when an atom in the gas phase accepts an electron. Cl(g) + e‒→ Cl‒(g)
Periodic Trends in Properties of Elements Electron Affinity (EA) is the energy released when an atom in the gas phase accepts an electron.
Periodic Trends in Properties of Elements It is easier to add an electron to an s orbital than to add one to a p orbital with the same principal quantum number.
Periodic Trends in Properties of Elements Within a p subshell, it is easier to add an electron to an empty orbital than to add one to an orbital that already contains an electron.
Periodic Trends in Properties of Elements More than one electron may be added to an atom. Process O(g) + e− → O−(g) O− (g) + e− → O 2−(g) ΔH (k. J/mol) − 141 744 Electron Affinity EA 1 = 141 k. J/mol EA 2 = − 741 k. J/mol A significantly endothermic process happens only in concert with one or more exothermic processes
Periodic Trends in Properties of Elements Metals tend to • Be shiny, lustrous and malleable • Be good conductors of heat and electricity • Have low ionization energies (form cations) • Form ionic compounds with chlorine (metal chlorides) • Form basic compounds with oxygen (metal oxides)
Periodic Trends in Properties of Elements Nonmetals tend to • Vary in color and are not shiny • Be brittle, rather than malleable • Be poor conductors of electricity • Form acidic, molecular compounds with oxygen • Have high electron affinities (form anions)
Periodic Trends in Properties of Elements Metalloids are elements with properties intermediate between those of metals and nonmetals.
7. 5 Electron Configurations of Ions To write the electron configuration of an ion formed by a main group element: 1) Write the configuration for the atom. 2) Add or remove the appropriate number of electrons. Na: 1 s 22 p 63 s 1 Na+: 1 s 22 p 6 10 electrons total, isoelectronic with Ne Cl: 1 s 22 p 63 s 23 p 5 Cl‒: 1 s 22 p 63 s 23 p 6 18 electrons total, isoelectronic with Ar
Electron Configurations of Ions of d-block elements are formed by removing electrons first from the shell with the highest value of n. Fe: [Ar]4 s 23 d 6 Fe 2+: [Ar]3 d 6 Fe: [Ar]4 s 23 d 6 Fe 3+: [Ar]3 d 5
7. 6 Ionic Radius The ionic radius is the radius of a cation or an anion. Cations are always smaller than their atoms. Anions are always larger than their atoms. The ionic radius affects physical and chemical properties of an ionic compound.
Ionic Radius An isoelectronic series is a series of two or more species that have identical electron configurations but different nuclear charges. O 2‒: 1 s 22 p 6 F‒: 1 s 22 p 6 isoelectronic Ne: 1 s 22 p 6
7. 7 Periodic Trends in Chemical Properties of the Main Group Elements IE and EA enable us to understand types of reactions that elements undergo and the types of compounds formed.
Periodic Trends in Chemical Properties of the Main Group Elements Hydrogen (1 s 1) • Grouped by itself • Forms a cation with a +1 charge (H+) • Forms an anion with a ‒ 1 charge (H‒) • Hydrides react with water to produce hydrogen gas and a base. Ca. H 2(s) + H 2 O(l) → Ca(OH)2(aq) + H 2(g)
Periodic Trends in Chemical Properties of the Main Group Elements Group 1 A elements (ns 1, n ≥ 2) • Low IE • Never found in nature in pure elemental state • React with oxygen to form metal oxides
Periodic Trends in Chemical Properties of the Main Group Elements Group 2 A elements (ns 2, n ≥ 2) • Less reactive than 1 A • Some react with H 2 O to produce H 2 • Some react with acid to produce H 2
Periodic Trends in Chemical Properties of the Main Group Elements Group 3 A elements (ns 2 np 1, n ≥ 2) • Metalloid (B) and metals (all others) • Al forms Al 2 O 3 with oxygen • Al forms +3 ions in acid • Others form +1 and +3
Periodic Trends in Chemical Properties of the Main Group Elements Group 4 A elements (ns 2 np 2, n ≥ 2) • Nonmetal (C); metalloids (Si, Ge) and others metals • Form +2 and +4 oxidation states • Sn, Pb react with acid to produce H 2
Periodic Trends in Chemical Properties of the Main Group Elements Group 5 A elements (ns 2 np 3, n ≥ 2) • Nonmetal (N 2, P) metalloid (As, Sb) and metal (Bi) • Nitrogen, N 2 forms variety of oxides • Phosphorus, P 4 • As, Sb, Bi (crystalline) • HNO 3 and H 3 PO 4 important industrially
Periodic Trends in Chemical Properties of the Main Group Elements Group 6 A elements (ns 2 np 4, n ≥ 2) • Nonmetals (O, S, Se) • Metalloids (Te, Po) • Oxygen, O 2 • Sulfur, S 8 • Selenium, Se 8 • Te, Po (crystalline) • SO 2, SO 3, H 2 SO 4
Periodic Trends in Chemical Properties of the Main Group Elements Group 7 A elements (ns 2 np 5, n ≥ 2) • All diatomic • Do not exist in elemental form in nature • Form ionic “salts” • Form molecular compounds with each other
Periodic Trends in Chemical Properties of the Main Group Elements Group 8 A elements (ns 2 np 6, n ≥ 2) • All monatomic • Filled valence shells • Considered “inert” until 1963 when Xe and Kr were used to form compounds • No major commercial use
Periodic Trends in Chemical Properties of the Main Group Elements Comparison of Group 1 A and Group 1 B Elements • Have single valence electron • Properties differ • Group 1 B much less reactive than 1 A • High IE of 1 B - incomplete shielding of nucleus by inner “d” - outer “s” electron of 1 B strongly attracted to nucleus • 1 B metals often found elemental in nature (coinage metals)
Periodic Trends in Chemical Properties of the Main Group Elements
7 Chapter Summary: Key Points Development of Periodic Table The Modern Periodic Table Classification of Elements Free Elements in Chemical Equations Effective Nuclear Charge Periodic Trends in Properties of Elements Atomic Radius Ionization Energy Electron Affinity Metallic Character Electron Configuration of Ions of Main Group Elements Ions of d-Block Elements Ionic Radius Comparing Ionic Radius with Atomic Radius Isoelectronic Series Periodic Trends in Chemical Properties of the Main Group Elements General Trends in Chemical Properties of the Active Metals Properties of Other Main Group Elements Comparison of Group 1 A and Group 1 B Elements Variation in Properties of Oxides Within a Period
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