Chem 161-2010 Lecture 18

Chem 161-2010 Lecture 18 - CHEMISTRY 161-2010 LECTURE 18...

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Chem 161Chem-2010 Lecture 18 1 CHEMISTRY 161-2010 LECTURE 18 ANNOUNCEMENTS ATTENDANCE QUIZZES EXAMS/QUIZZES MISCELLANEOUS LECTURE QUIZ?
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Chem 161Chem-2010 Lecture 18 2 PLAN FOR TODAY : H&P CHAPTER SECTIONS 9.7 – 9.9 • BOND POLARITY AND DIPOLE MOMENTS -- Electronegativity -- Ions and ionic bonding LEWIS STRUCTURES FORMAL CHARGE RESONANCE STRUCTURES
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Chem 161Chem-2010 Lecture 18 3 FACTORS GOVERNING PERIODIC TABLE TRENDS (1) Increasing valence principle shell number (with same effective nuclear charge) less attraction of valence electrons to nucleus (2) Increasing effective nuclear charge (with same number of principal shells) Greater attraction of valence electrons to nucleus. Isoelectronic series follows “Z” pattern for size of atoms/ions. (3) Increasing electrons in valence shell (with same number of principal shells and same effective nuclear charge) Greater electron repulsion (4) Exceptions: Ionization energy and electron affinity o Nearest neighbor atoms ionization energies and electron affinities, due mainly to subshell influences. Ionization energies: , e.g., 5 B vs 4 Be [p vs s], 8 O vs 7 N [filled p orbital vs half-filled p orbital Electron affinities: e.g., formation of 6 C - vs 7 N - ; also electron repulsion in smaller atoms, e.g., 6 O vs. 16 S. (o First separate effects of atoms/ions based on degree of ionization energy or electron affinity (i.e., 3 rd IE > 2 nd IE > 1 st IE; 3 rd EA > 2 nd EA > 1 st EA). Then follow rules 1 to 3 for the separated groups.) INCREASING PRIORITY
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Chem 161Chem-2010 Lecture 18 4 SMALLER ATOM SMALLER ION MORE ENDOTH. FIRST IONIZATION ENERGY MORE EXOTH. FIRST ELECTRON AFFINITY GREATER ELECTRONEGATIVITY LESS METALLIC PROPERTY GOOD REDUCTION GOOD OXIDIZING AG’T ACIDIC OXIDES PERIODIC TABLE AND PERIODIC PROPERTIES
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Chem 161Chem-2010 Lecture 18 5 CHAPTER 9 ELECTRONEGATIVITY PERIODIC TABLE 1A 2A 3B 4B 5B 6B 7B 8B 8B 8B 1B 2B 3A 4A 5A 6A 7A 8A H 2.1 He Li 1.0 Be 1.5 B 2.0 C 2.5 N 3.0 O 3.5 F 4.0 Ne Na 0.9 Mg 1.2 A l 1.5 Si 1.8 P 2.1 S 2.5 Cl 3.0 Ar K 0.8 Ca 1.0 Sc 1.3 Ti 1.5 V 1.6 Cr 1.6 Mn 1.5 Fe 1.8 Co 1.8 Ni 1.8 Cu 1.9 Zn 1.7 Ga 1.6 Ge 1.8 As 2.0 Se 2.4 Br 2.8 Kr Rb 0.8 Sr 1.0 Y 1.2 Zr 1.4 Nb 1.5 Mo 1.8 Tc 1.9 Ru 2.2 Rh 2.2 Pd 2.2 Ag 1.9 Cd 1.7 In 1.7 Sn 1.8 Sb 1.9 Te 2.1 I 2.5 Xe Cs 0.7 Ba 0.9 La 1.1 Ce Pr Nd Pm Sm Eu Gd Tb Tl 1.8 Pb 1.8 Bi 1.9 Po 2.0 At 2.2 Rn Fr 0.7 Ra 0.9 Ac 1.1 Th Pa U Np Pu
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Chem 161-2010 Lecture 18 6 CHAPTER 9: BONDING: GENERAL CONCEPTS ELECTRONEGATIVITY, BOND POLARITY AND DIPOLES ET: Electronegativity definition: The tendency of an element, in molecules, to attract electrons to itself. Very closely related to electron affinity in individual atoms.
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Chem 161-2010 Lecture 18 - CHEMISTRY 161-2010 LECTURE 18...

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