Chem 161-2010 Lecture 16

Chem 161-2010 Lecture 16 - CHEMISTRY 161-2010 LECTURE 16...

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CHEMISTRY 161-2010 LECTURE 16 ATTENDANCE E-MAIL MISCELLANEOUS EXAMS Chem 161-2010 Lecture 16 1
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PLAN FOR TODAY : • PERIODIC TABLE AND PERIODIC PROPERTIES -- Atomic and ionic radius -- Ionization energy -- Electron affinity -- Oxidation and reduction potential Chem 161-2010 Lecture 16 2
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AUFBAU PRINCIPLE -- ORDER OF SUBSHELLS ET: “Aufbau” meams “building up” in German 1s 2 ( 2 He) 2s 2 2p 6 ( 10 Ne) 3s 2 3p 6 3d 10 ( 18 Ar) 4s 2 4p 6 4d 10 4f 14 ( 36 Kr) 5s 2 5p 6 5d 10 5f 14 ( 54 Xe) 6s 2 6p 6 6d 10 6f 14 ( 86 Rn) 7s 2 7p 6 7d 10 7f 14 ( 118 Uuo) 8s 2 8p 6 8d 10 8f 14 Chem 161-2010 Lecture 16 3
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Chem 161-2010 Lecture 16 4 SMALLER ATOM SMALLER ION MORE ENDOTH. FIRST IONIZATION ENERGY MORE EXOTH. FIRST ELECTRON AFFINITY GREATER ELECTRONEGATIVITY LESS METALLIC PROPERTY GOOD REDUCTION POOR OXIDATION ACIDIC OXIDES PERIODIC TABLE AND PERIODIC PROPERTIES
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Chem 161-2010 Lecture 16 5 3s ORBITAL ELECTRON DISTRIBUTION
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ET: Understanding what “effective nuclear charge” is. Chem 161-2010 Lecture 16 6 FACTORS GOVERNING PERIODIC TABLE TRENDS EFFECTIVE NUCLEAR CHARGE 17 Cl=1s 2 2s 2 2p 6 3s 2 3p 5 Effective nuclear charge = +7 17+ 17+ 7+ 7- 8- 2- 7- 8- 2- Valence electrons Core electrons Total nuclear charge X X X
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FACTORS GOVERNING PE RIODIC TABLE TRENDS (1) Increasing valence principle shell number → 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.) Chem 161-2010 Lecture 16 7 INCREASING PRIORITY
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Chem 161-2010 Lecture 16 8
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Chem 161-2010 Lecture 16 9
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H & P 51. Arrange the set in order of increasing radius, and explain the basis for this order. Al, B, K, Mg 13 Al = 1s 2 2s 2 2p 6 3s 2 3p 1 5 B = 1s 2 2s 2 2p 1 19 K = 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 12 Mg = 1s 2 2s 2 2p 6 3s 2 B has only two occupied principal shells, so it is the smallest. Al and Mg both have the same number of occupied principal shells, but Al has a large ENC, so it is the next smallest. K has the greatest number of principal shells, so it is the largest. B < Al < Mg < K
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Chem 161-2010 Lecture 16 - CHEMISTRY 161-2010 LECTURE 16...

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