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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. PowerPoint to accompany General Chemistry Third Edition Chapter 8 Raymond Chang
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Problems from pages 1-8, 10-14, 18, 20, 22-24, 26, 28, 30, 32-35, 38, 40, 42, 44, 46, 49, 50, 52, 53, 54, 66, 70, 72, 84,
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EH Assignment Due April 1 Unit 9 Minimum score Sec 1 already done Sec 2 90 Sec 3 Sec 4 Sec 5 Sec 6
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Test on Chapters 7 and 8 April 6
EH Assignment Due April 4 Unit 11 Minimum score Sec 1 90 Sec 2 Sec 3 Sec 4 Sec 5 75 Test on Chapters 7 and 8 April 6
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Development of the Periodic Table
In 1870 the Russian chemistry Dmitri Mendeleev arranged the 65 known elements into a periodic table. The periodic law: when the elements are arranged by atomic mass similar properties recur periodically. Mendeleev placed elements with similar properties in the same column. But he had to make the rows of unequal length and leave gaps to make similar properties line up.
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Ground State Electron Configurations of the Elements
ns2np6 Ground State Electron Configurations of the Elements ns1 ns2np1 ns2np2 ns2np3 ns2np4 ns2np5 ns2 d10 d1 d5 4f 5f 8.2
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Fig. 8.2
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Valence Electrons 1. Inner (core) electrons are those in the previous
noble gas and any completed transition series. 2. Outer electrons are those in the highest energy level (highest n value). 3. Valence electrons are the outer electrons for the representative elements. The number of valence electrons can easily be determined from the position in the periodic table. 4. For the transition and inner transition elements the concept of valence electron is not useful. Examples: sodium, chlorine
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Electron Configurations of
Metal Ions All metals lose electrons to form cations. Many of the metals which are representative elements lose all their valence electrons to have noble gas configurations. Transition metal ions rarely attain a noble gas configuration. They always lose the outer s electrons first. Usually they lose one or more d electrons as well. Example: Fe (how many unpaired electrons?)
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Electron Configurations of
Transition Metal Ions Predict if the following are paramagnetic or diamagnetic? Sc Mn Zn2+
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Electron Configurations of Cations and Anions
Of Representative Elements Na [Ne]3s1 Na+ [Ne] Metals lose electrons. Ca [Ar]4s2 Ca2+ [Ar] Al [Ne]3s23p1 Al3+ [Ne] H 1s1 H- 1s2 or [He] Many nonmetals gain electrons so the anion has a noble-gas outer electron configuration. F 1s22s22p5 F- 1s22s22p6 or [Ne] O 1s22s22p4 O2- 1s22s22p6 or [Ne] N 1s22s22p3 N3- 1s22s22p6 or [Ne] 8.2
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Na+, Al3+, F-, O2-, and N3- are all isoelectronic with Ne
Na+: [Ne] Al3+: [Ne] F-: 1s22s22p6 or [Ne] O2-: 1s22s22p6 or [Ne] N3-: 1s22s22p6 or [Ne] Na+, Al3+, F-, O2-, and N3- are all isoelectronic with Ne What neutral atom is isoelectronic with H- ? 8.2
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Trends in Key Periodic Atomic Properties
Atomic Size: There is no real limit to how far an electron can be away from the nucleus. But, atomic size is a measurable quantity. In practice we measure the distance between two identical, adjacent atomic nuclei and divide distance in half. Many of the properties of elements are related to the size of their atoms.
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Fig. 8.11
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Fig. 8.4
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Fig. 8.5
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Ranking Elements by Size
Problem: Rank the following elements in each up according to decreasing size ( largest first!): a) Na, K, Rb b) Sr, In, Rb c) Cl, Ar, K d) Sr, Ca, Rb
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0 < s < Z (s = shielding constant)
Effective nuclear charge (Zeff) is the “positive charge” felt by an electron. Zeff = Z - s 0 < s < Z (s = shielding constant) Zeff Z – number of inner or core electrons Zeff Core Z Radius Na Mg Al Si 11 12 13 14 10 1 2 3 4 186 160 143 132 Within a Period as Zeff increases radius decreases 8.3
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TA p237
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Cation is always smaller than atom from which it is formed.
Anion is always larger than atom from which it is formed. 8.3
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8.3
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Fig. 8.6
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There is a rough inverse correlation between I1 and atomic radius.
Ionization energy is the minimum energy (kJ/mol) required to remove an electron from a gaseous atom in its ground state. I1 + X (g) X+(g) + e- I1 first ionization energy I2 + X+(g) X2+(g) + e- I2 second ionization energy I3 + X2+(g) X3+(g) + e- I3 third ionization energy I1 < I2 < I3 There is a rough inverse correlation between I1 and atomic radius. 8.4
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8.4 Filled n=1 shell Filled n=2 shell Filled n=3 shell
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General Trend in First Ionization Energies
Increasing First Ionization Energy Increasing First Ionization Energy 8.4
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Fig. 8.15
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Problem: Using the Periodic table only, rank the
Ranking Elements by First Ionization Energy Problem: Using the Periodic table only, rank the following elements in each of the following sets in order of increasing I1 a) Ar, Ne, Rn b) At, Bi, Po c) Be, Na, Mg d) Cl, K, Ar
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Fig. 8.16
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Identifying Elements by Its Successive Ionization Energies
Problem: Given the following series of ionization energies (in kJ/mol) for an element in period 3, name the element and write its electron configuration: I I I I4 , , ,600
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Electron affinity is the negative of the energy change that occurs when an electron is accepted by an atom in the gaseous state to form an anion. X (g) + e X-(g) F (g) + e F-(g) DH = -328 kJ/mol EA = +328 kJ/mol O (g) + e O-(g) DH = -141 kJ/mol EA = +141 kJ/mol 8.5
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Trends in Metallic Behavior
Fig. 8.19
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Group 1A Elements (ns1, n 2)
M M+1 + 1e- 2M(s) + 2H2O(l) MOH(aq) + H2(g) 4M(s) + O2(g) M2O(s) Increasing reactivity 8.6
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Group 2A Elements (ns2, n 2)
M M+2 + 2e- Be(s) + 2H2O(l) No Reaction Mg(s) + 2H2O(g) Mg(OH)2(aq) + H2(g) M(s) + 2H2O(l) M(OH)2(aq) + H2(g) M = Ca, Sr, or Ba Increasing reactivity 8.6
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Metal oxides tend to be basic.
Non metal oxides tend to be acidic. Amphoteric oxides exhibit both acidic and basic properties.
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The Trends in Acid-Base Behavior of Elemental Oxides
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