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Lecture March 13

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Chapter 9 - Chemical Bonding I

Lewis TheoryNext Mastering Chemistry HW and Quiz

Chap 4 (II) will be due March 27th

Hopefully will post MC by the break

Remember any regrades due by tomorrowafternoon at 5 PM

Finish Oxidation-Reduction Reactions -Sec. 4.9

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Review of Oxidation

Numbers

2

4 FeCO3(s) + O2(g) !2 Fe2O3(s) + 4 CO2(g)

Use the chargeon a CO32-

Fe is +2 Fe is +3 O is -2

Fe +2 to +3 oxidized

O from 0 to -2 reduced

O is 0

FeCO3is the REDUCING AGENT

O2is the OXIDIZING AGENT

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Last Example

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The oxidation number of an ion is the ion charge

2Al(s) + 3Cu2+(aq) !2Al3+(aq) + 3Cu(s)

Al 0 to 3+

Cu 2+ to 0

Balancing the ox #2 x +3 = +63 x -2 = -6

Al is oxidized reducing agent

Cu2+is reduced oxidizing agent

OIL RIG

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Review Valence Electrons

4

Remember -Valence electrons in main groupelements

the s and p electrons in the outermost shell

1A ns1 (1)2A ns2 (2)

3A ns2np1(3)4A ns2np2(4)5A ns2np3(5)

6A

ns2

np4

(6)7A ns2np5(7)8A ns2np6(8)

This isequal to

the groupnumber

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Lewis Dot Structures

5

Use a #to represent a valence electron

For Period 1, 2,and 3

H#

He#

#

B# ##

Be# # C#

#

#

# N ##

#

#

#

Li# F#

O#

#

#

#

#

#

#

#

#

#

Valence electrons make the bonds

##

Mg# # Al

#

## Si ##

#

#Na# #

#P##

#

#

#S

#

#

#

# Cl

#

#

#

#

#

## Ar#

#

#

###

##

Ne##

#

###

##

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Covalent Bonds

7

Electrons are sharedbetween the two atoms

Goal is to complete the OCTET(noblegas configuration) by sharing electrons

Exceptions: less that an octetH (2 electrons !He)BeB

Expanded Octet using the d orbitalsfor elements with n = 3 or greater

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Single Covalent Bonds

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Simple Compounds satisfying the octet rule:

CH4 NH3 H2O HF

HCl

H2Exception

Cl2

CH3Cl

CH2Cl2 CH2ClF

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Multiple Bonds

9

O2 N2double bond triple bonds

Very common among C, N, and O

CH3COOH acetic acid

CO2 O3 Resonance structure

CO

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Electron Deficient

Structures

10

With Be (2 valence electrons) andB (3 valence electrons)

BeCl2 BCl3

Unpaired electrons - radicals -

odd number of valence electrons

NO NO2 Very Reactive

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Lewis Structures of Ions

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Common ions:

NH4+Adding H+

H3O+Removing H+

CH3COO- acetate ion

ammonium ion

hydronium ion

OH- hydroxide ion

NO3- nitrate ion

(acids)

(bases)

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Quiz of the Day

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For the following reaction, determine thechange in oxidation number for the Fe

4 FeO(s) + O2(g) + 6H2O(l) !4 Fe(OH)3(s)

Express your answer as the first one , thesecond one with no spaces and include

the sign.

For example an answer might be0,-2

Answer: +2,+3