Chapter 7_May11 - CHAPTER7 PeriodicPropertiesofthe Elements...

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1 CHAPTER 7 CHAPTER 7 Periodic Properties of the  Elements
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2 CONTENT CONTENT 7.1 Development of the Periodic Table 7.2 Effective nuclear charge and the Sizes of Atoms 7.3 Ionization Energy 7.4 Electron Affinities 7.5 Metals, Nonmetals, and Metalloids 7.6 Group Trends for the Active Metals 7.7 Group Trends for Selected Nonmetals
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3 Learning outcomes Able to relate effective nuclear charge to size, ionization energy and electron affinity of elements in periodic table To differentiate metal , non-metal and metalloid
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4 7.1 Development of The Periodic  7.1 Development of The Periodic  Table Table The periodic table was first developed by Mendeleev and Meyer  on the basis of the similarity in properties and reactivities  exhibited by certain elements. Elements in the same column of the periodic table have the  same number of electrons in their valence orbitals.
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5 Con’t: 7.1 Development of The  Con’t: 7.1 Development of The  Periodic Table Periodic Table Group 1A : Group 6A : 3 Li - [He] 2s  1 8 O - [He] 2s  2  2p  4 11 Na- [Ne] 3s  1 16 S - [Ne] 3s  2  3p  4 19 K - [Ar] 4s  1 37 Rb- [Kr] 5s  1
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6 7.2  Effective Nuclear Charge and  7.2  Effective Nuclear Charge and  Sizes of Atoms Sizes of Atoms 7.2.1 Effective Nuclear Charge The net positive charge experienced by an electron on a many-electron atom. Not the same as the charge on the nucleus because of the effect of the inner electrons. The electron is attracted to the nucleus, but repelled by the inner-shell electrons that shield or screen it from the full nuclear charge.
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7 Con’t: 7.2.1 Effective Nuclear Charge The shielding effect is called the screening effect . The nuclear charge experienced by an electron depends on its distance from the nucleus and also the screening effect. Z eff = Z – S
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8 The principal quantum number, n, of the valence  orbitals of the atoms changes from top to bottom of  the Periodic Table. All orbitals with the same value of n are referred to  as a  shell . 7.2.2 Electron Shells in Atoms 7.2.2 Electron Shells in Atoms
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9 Con’t: 7.2.2 Electron Shells in Atoms Con’t: 7.2.2 Electron Shells in Atoms Consider the noble gases: Nuclear charge He 1s  2 2+ Ne 1s  2  2s  2  2p  6 10+ Ar 1s  2  2s  2  2p  6  3s  2  3p  6 18+ Plot radial electron-density graph for electron distribution in  these atoms.
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10 Con’t:
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11 The  maxima  (peaks) appear based on electrons having the same  quantum number,  n. n = 1 - 1  peak (1s) Con’t: 7.2.2 Electron Shells in Atoms Con’t: 7.2.2 Electron Shells in Atoms
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12 From the graph: 1s electrons for Helium show a maximum in radial electron  density - 0.3 Å 1s electrons for Argon - 0.05 Å only Con’t: 7.2.2 Electron Shells in Atoms Con’t: 7.2.2 Electron Shells in Atoms
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This note was uploaded on 06/16/2011 for the course ENGR 101 taught by Professor Ahmed during the Summer '11 term at Multimedia University, Cyberjaya.

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Chapter 7_May11 - CHAPTER7 PeriodicPropertiesofthe Elements...

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