Welcome to 3.091Lecture 9

September 28, 2009

Drawing Lewis Structures

Cl_

Cl_

Cl_

Na+

Na+

Na+ Cl_r = 236

r = 600

r = 180

Pote

ntia

l ene

rgy

(kJ/

mol

)

Internuclear distance, r (pm) 0

-589

r0

6 < n < 12

EαH = _ e2

4π o r

Erep = brn Born exponent

Repulsive interactionsAttractive interactionsTotal energy

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Public domain image from Wikipedia.

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3A(13) 4A(14) 5A(15) 6A(16) 7A(17) 8A(18)1A(1)

2

3

2A(2)

ns1 ns2 ns2np1 ns2np2 ns2np3 ns2np4 ns2np5 ns2np6

B C N O F Ne

Al Si

Li Be

Na Mg P S Cl Ar

Perio

d

Lewis Notation: Electron - Symbols (1916)

Element symbol Nucleus & inner es Dots Valence es

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Electronegativity χ

23

45 s

pMetal have low χ

Nonmetals have high χ

Copyright © 2003 John Wiley & Sons, Inc. Reprinted with permission of John Wiley & Sons., Inc. Source: Spencer, J. N., G. M. Bodner, and L. H. Rickard. Chemistry: Structure and Dynamics. 2nd edition. New York, NY: John Wiley & Sons, 2003.

4.0

3.0

2.0

1.0

0100 20 30 40 50 60 70 80 90

Elec

trone

gativ

ity, χ

Atomic number

Main groups 1-2 (s block) Main groups 13-18 (s block)

Lanthanides (f block)Transition metals (d block)

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H

Li

Na

K

Rb

Cs Ba La Hf Ta

Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

LrNoMdFmEsCfBkCmAmPuNpUPaTh

W Re Os Ir Pt Au Hg Tl Pb Bi Po Rn

UupUuqUutUubRgMtHsBhSgDbRfAcRaFr Ds

Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe

Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga

B

Al Si Ar

O F Ne

He

Ge Se KrAs

C N

P S Cl

At

Br

Mg

2.20

0.98

0.93 1.31

0.82 1.00 1.36 1.54

1.33

1.3

1.63

1.6

1.5

1.66

2.16

1.7

1.55

2.10

1.9

1.83

2.2

2.2

1.88

2.28

2.2

1.91

2.20

2.2

1.90

1.93

2.4

1.65

1.69

1.9

1.81

1.78

1.8

2.04

1.61

2.01

1.96

1.8

2.55

1.90

2.18

2.05

1.9

3.04

2.19

2.55

2.1

2.0

3.44

2.58

2.96

2.66

2.2

3.98

3.16

1.22

1.10

1.12

1.3

1.13

1.5

1.14

1.7 1.3 1.3

1.17 1.20 1.22 1.23 1.24 1.25 1.0

1.1

0.95

0.89

0.9

0.82

0.79

0.7

1.57

Be2

3 4 5 6 7 8 9 10 11 12

13 14 15 16 17

181

2

3

4

5

6

7

1

0.7 3.98

Lanthanides

Actinides

6

7

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Increasing

Electronegativity, χ

Incr

easi

ng

s Block p Block d Block f Block

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© source unknown. All rights reserved. This image is excluded from our Creative Commons license. For more information, see http://ocw.mit.edu/fairuse.

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Figure removed due to copyright restrictions.Chandler, David L. "MIT scientist shares Nobelfor identifying ozone damage." The Boston Globe,October 12, 1995.

Nature, 249 June 28, 1974

Reprinted by permission from Macmillan Publishers Ltd: Nature © 1974. Source: Molina, Mario J., and Rowland, F. S. "Stratospheric sink for chlorofluoromethanes: chlorine atomc-atalysed destruction of ozone." Nature 249 (June 28, 1974): 810-812.

.

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