Electron Configuration and the Periodic Table Chemistry Second Edition Julia Burdge Lecture PowerPoints Jason A. Kautz University of Nebraska-Lincoln 7 Electron Configuration and the Periodic Table 1 Copyright (c) The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Electron Configuration and the Periodic Table 7 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 Ions of Main Group Elements Ions of d-Block Elements 7.6 Ionic Radius Comparing Ionic Radius with Atomic Radius Isoelectronic Series

Electron Configuration and the Periodic Table 7 7.7 Periodic Trends in Chemical Properties of the Main Group Elements General Trends in Chemical Properties Properties of the Active Metals Properties of Other Main Group Elements Comparison of Group 1A and Group 1B Elements Variation in Properties of Oxides Within a Period

Development of the Periodic Table 7.1 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.

The Modern Periodic Table 7.2

The Modern Periodic Table The main group elements (also called the representative elements) are the elements in Groups 1A through 7A.

The Modern Periodic Table The noble gases are found in Group 8A.

The Modern Periodic Table The transition metals are found in Group 1B and 3B through 8B. Group 2B 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 1A: [noble gas]ns1 For Group 2A: [noble gas]ns2

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 1A: [noble gas]ns1 valence core For Group 2A: [noble gas]ns2 valence core For Group 7A: [noble gas]ns2np5 valence core

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 (H2, N2, O2, F2, Cl2, Br2, I2, and P4). Sulfur is usually written as S instead of S8 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)

Effective Nuclear Charge 7.3 Effective Nuclear Charge (Zeff) is the actual magnitude of positive charge that is experienced by an electron in the atom. 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 Zeff = Z – σ Li Be B C N O F Z 3 4 5 6 7 8 9 Zeff 1.28 1.91 2.42 3.14 3.83 4.45 5.10

Effective Nuclear Charge Effective Nuclear Charge (Zeff) is the actual magnitude of positive charge that is experienced by an electron in the atom. Zeff = Z – σ

Periodic Trends in Properties of Elements 7.4 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. IE1(Na) = 495.8 kJ/mol. Na(g) → Na+(g) + e−

Periodic Trends in Properties of Elements IE1 value for the main group elements (kJ/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. IE1(Na) = 496 kJ/mol. IE2(Na) = 4562 kJ/mol. Na(g) → Na+(g) + e− Na+(g) → Na2+(g) + e−

Periodic Trends in Properties of Elements It takes more energy to remove the 2nd, 3rd, 4th, 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 ΔH (kJ/mol) Electron Affinity O(g) + e− → O−(g) −141 EA1 = 141 kJ/mol O− (g) + e− → O2−(g) 744 EA2 = −741 kJ/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.

Electron Configurations of Ions 7.5 To write the electron configuration of an ion formed by a main group element: Write the configuration for the atom. Add or remove the appropriate number of electrons. Na: 1s22s22p63s1 Na+: 1s22s22p6 10 electrons total, isoelectronic with Ne Cl: 1s22s22p63s23p5 Cl‒: 1s22s22p63s23p6 18 electrons total, isoelectronic with Ar

Electron Configurations of Ions Ions of d-block elements are formed by removing electrons first from the shell with the highest value of n. Fe: [Ar]4s23d 6 Fe2+: [Ar]3d 6 Fe: [Ar]4s23d 6 Fe3+: [Ar]3d 5

Ionic Radius 7.6 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.

O2‒: 1s22s22p6 F‒: 1s22s22p6 Ne: 1s22s22p6 Ionic Radius An isoelectronic series is a series of two or more species that have identical electron configurations but different nuclear charges. O2‒: 1s22s22p6 F‒: 1s22s22p6 Ne: 1s22s22p6 isoelectronic

Periodic Trends in Chemical Properties of the Main Group Elements 7.7 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 (1s1) 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. CaH2(s) + H2O(l) → Ca(OH)2(aq) + H2(g)

Periodic Trends in Chemical Properties of the Main Group Elements Group 1A elements (ns1, 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 2A elements (ns2, n ≥ 2) Less reactive than 1A Some react with H2O to produce H2 Some react with acid to produce H2

Periodic Trends in Chemical Properties of the Main Group Elements Group 3A elements (ns2np1, n ≥ 2) Metalloid (B) and metals (all others) Al forms Al2O3 with oxygen Al forms +3 ions in acid Others form +1 and +3

Periodic Trends in Chemical Properties of the Main Group Elements Group 4A elements (ns2np2, n ≥ 2) Nonmetal (C); metalloids (Si, Ge) and others metals Form +2 and +4 oxidation states Sn, Pb react with acid to produce H2

Periodic Trends in Chemical Properties of the Main Group Elements Group 5A elements (ns2np3, n ≥ 2) Nonmetal (N2, P) metalloid (As, Sb) and metal (Bi) Nitrogen, N2 forms variety of oxides Phosphorus, P4 As, Sb, Bi (crystalline) HNO3 and H3PO4 important industrially

Periodic Trends in Chemical Properties of the Main Group Elements Group 6A elements (ns2np4, n ≥ 2) Nonmetals (O, S, Se) Metalloids (Te, Po) Oxygen, O2 Sulfur, S8 Selenium, Se8 Te, Po (crystalline) SO2, SO3, H2S, H2SO4

Periodic Trends in Chemical Properties of the Main Group Elements Group 7A elements (ns2np5, 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 8A elements (ns2np6, 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 1A and Group 1B Elements Have single valence electron Properties differ Group 1B much less reactive than 1A High IE of 1B - incomplete shielding of nucleus by inner “d” - outer “s” electron of 1B strongly attracted to nucleus 1B metals often found elemental in nature (coinage metals)

Periodic Trends in Chemical Properties of the Main Group Elements

Chapter Summary: Key Points 7 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 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 Properties of the Active Metals Properties of Other Main Group Elements Comparison of Group 1A and Group 1B Elements Variation in Properties of Oxides Within a Period