chapt7yp - CHAPTER 7 The Structure o f A toms a nd Periodic...

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CHAPTER 7 The Structure of Atoms and Periodic Trends I. Electron Configurations & the Aufbau Principle II. Electron Configurations & the Periodic Table III. Atomic Properties & Periodic Trends I. Electron Configurations and the Aufbau Principle A. General 1. Electron configuration is how the electrons are distributed among the various atomic orbitals in an atom. 2. Orbital box diagrams use boxes to represent orbitals and arrows to represent electrons. H IT] 1 S1 1
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B. Pauli Exclusion Principle 1. Pauli exclusion principle states that no two electrons in an atom can have the same four quantum numbers. 2. As there are only two possible values for m s (+Y2 or -Y2) an orbital can only accommodate a maximum of two electrons of opposite spin. subshell # orbitals max. # e- s (1=0) p (1=1) d (1=2) f (1=3) c. Building-Up Principle - Aufbau Principle 1. Electrons occupy orbitals of the lowest energy available and fill in the following order: 1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s 2
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2. Electron configurations of the 'first fifteen elements: 1 H 1s 1 2 He 1s 2 3Li 2 2s 1 4 Be 2 2 s8 1S2 2s 2 2p1 6 C 1S2 2s 2 2p2 7 N 2 2 2p3 80 1S2 2s 2 2p4 gF 1S2 2s 2 2 p s 10 Ne 1S2 2s 2 2p 6 11 Na 1S2 2s 2 6 3s 1 12Mg 2 2 6 3s 2 13AI 1S2 2s 2 2p 6 2 3p 1 14Si 2 2 6 2 3p2 1SP 1s 2 2 6 3s 2 3p3 3. Abbreviated noble-gas core electron configurations:- 3 Li 1S2 2s 1 or 1S2 2s 2 2p4 12 M g 1S2 2s 2 2p 6 2 1SP 1S2 2s 2 2p 6 3s 2 3p3 or 4. Hund's Rule: Electrons enter unoccupied orbitals first before pairing. 5. Orbital box diagran1s of selected elements: 3 3
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6. Diamagnetism and Paramagnetism:- The magnetic properties of a substance can reveal certain information about the arrangement of electrons in an atom. Paramagnetic:- a substance that is weakly attracted by a magnetic field. Diamagnetic:- a substance that is slightly repelled by a magnetic field. t t t ~ Paramagnetic Diamagnetic unpaired electrons all electrons paired LL_ 111111 2p 2p What is the electron configuration of K ? What are the possible quantum numbers for the last (outermost) electron in CI ?
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This note was uploaded on 03/02/2010 for the course CHEM 210 taught by Professor Paukstelis during the Spring '09 term at Kansas State University.

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chapt7yp - CHAPTER 7 The Structure o f A toms a nd Periodic...

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