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Figure 9.11: Potential-energy curve for H 2 . - PowerPoint PPT Presentation


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Figure 9.11: Potential-energy curve for H 2 . Covalent Bonding in Hydrogen, H 2. For animation, open, then click on "reaction of sodium with chlorine“ Then choose “magnify the reaction. Figure 9.10: The electron probability distribution for the H 2 molecule.

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slide5

For animation, open, then click on "reaction of sodium with chlorine“

Then choose “magnify the reaction.

figure 9 10 the electron probability distribution for the h 2 molecule
Figure 9.10: The electron probability distribution for the H2 molecule.

Animation and choose covalent bonding between hydrogens

slide7

Covalent bonds

http://wine1.sb.fsu.edu/chm1045/notes/Bonding/Covalent/Bond04.htm

animation

http://www.chem.ox.ac.uk/vrchemistry/electronsandbonds/intro1.htm

slide8

For elements larger than Boron, atoms usually react to

develop octets by sharing electrons. H, Li and Be strive

to “look” like He. B is an exception to the noble gas paradigm.

It’s happy surrounded by 6 electrons so the compound BH3 is

stable.

Try drawing a Lewis structure for methane.

slide9

Draw Lewis dot structures for the halogens.

Notice that these all follow the octet rule!

Try oxygen and nitrogen.

These also follow the octet rule!

figure 9 12 molecular model of nitroglycerin
Figure 9.12: Molecular model of nitroglycerin.

What is the formula for this

compound?

slide12

Rules for drawing Lewis structures

1. Count up all the valence electrons

2. Arrange the atoms in a skeleton

3. Have all atoms develop octets (except

those around He)

slide18

Rules for drawing Lewis structures

1. Count up all the valence electrons

2. Arrange the atoms in a skeleton

3. Have all atoms develop octets (except

those around He)

4. Satisfy bonding preferences!

slide19

Draw a Lewis structure for C2H4

Draw a Lewis structure for C2H2

Try COCl2

slide25

The Relation of Bond Order,Bond Length and Bond Energy

Bond Bond Order Average Bond Average Bond

Length (pm) Energy (kJ/mol)

C O 1 143 358

C O 2 123 745

C O 3 113 1070

C C 1 154 347

C C 2 134 614

C C 3 121 839

N N 1 146 160

N N 2 122 418

N N 3 110 945

Table 9.4

slide30

Determining Bond Polarity from

Electronegativity Values

Problem: (a)Indicate the polarity of the following bonds with a polarity

arrow: O - H, O - Cl, C - N, P - N, N - S, C - Br, As - S

(b) rank those bonds in order of increasing polarity.

Plan: (a) We use Fig. 9.16 to find the EN values, and point the arrow

toward the negative end. (b) Use the EN values.

Solution:

a) the EN of O = 3.5 and of H = 2.1: O - H

the EN of O = 3.5 and of Cl = 3.0: O - Cl

the EN of C = 2.5 and of P = 2.1: C - P

the EN of P = 2.1 and of N = 3.0: P - N

the EN of N = 3.0 and of S = 2.1: N - S

the EN of C = 2.5 and of Br = 2.8: C - Br

the EN of As = 2.0 and of O = 3.5: As - O

b) C - Br < C - P < O - Cl < P - N < N - S < O - H < As - O

0.3 < 0.4 < 0.5 < 0.9 < 0.9 < 1.4 < 1.5

lewis structures of simple molecules
Lewis Structures of Simple Molecules

H

H

C

H

H

..

..

F

..

..

..

F

C

F

..

..

..

..

F

H

H

..

CH4

..

H

C

C

O

H

Methane

H

H

Ethyl Alcohol (Ethanol)

..

..

..

..

O

K+

..

Cl

..

..

..

..

..

..

O

O

..

CF4

..

KClO3

Potassium Chlorate

Carbon Tetrafluoride

slide35

Resonance:

Delocalized Electron-Pair Bonding - I

Ozone : O3

..

..

..

..

..

O

O

..

..

..

..

..

..

O

O

O

O

..

II

I

Resonance Hybrid Structure

..

O

..

..

..

..

O

O

One pair of electron’s resonances

between the two locations!!

slide36

Resonance:

Delocalized Electron-Pair Bonding - II

H

H

C

C

H

H

C

C

C

C

H

H

C

C

H

H

C

C

H

H

H

C

C

C

H

H

C

H

H

C

H

C

C

H

C

Benzene

Resonance Structure

H

lewis structures of simple molecules37
Lewis Structures of Simple Molecules

Resonance Structures -III

Nitrate

..

..

..

O

N

..

..

..

..

..

O

O

..

..

..

O

..

..

O

N

N

..

..

..

..

..

..

..

O

O

..

..

..

..

O

O

slide38

..

..

Cl

..

..

B

..

..

..

..

Cl

Cl

Lewis Structures for Octet Rule Exceptions

..

..

..

..

..

..

F

..

..

..

..

F

Cl

..

..

F

Each chlorine atom has

8 electrons associated.

Boron has only 6!

Each fluorine atom has

8 electrons associated.

Chlorine has 10 electrons!

.

..

..

..

..

..

..

N

..

..

..

..

Cl

Be

Cl

..

O

O

Each chlorine atom has

8 electrons associated. The

beryllium has only 4 electrons.

NO2 is an odd electron atom.

The nitrogen has 7 electrons.

slide39

Resonance Structures -

Expanded Valence Shells

..

..

O

O

..

..

..

..

H

O

S

O

H

H

O

S

O

H

..

..

O

O

..

..

..

..

..

..

..

..

..

..

..

..

..

..

F

F

F

F

..

..

..

..

..

..

..

F

S

F

P

..

..

F

..

F

..

..

..

..

..

..

..

..

F

F

..

F

p = 10e-

S = 12e-

Sulfur hexafluoride

Phosphorous pentafluoride

..

..

..

..

..

Resonance Structures

..

..

..

..

..

Sulfuric acid

S = 12e-

lewis structures of simple molecules40
Lewis Structures of Simple Molecules

. .

Sulfate

. .

-2

O

. .

. .

Resonance Structures-V

. .

. .

O

S

O

. .

. .

-2

. .

. .

O

o *

o o

o o

O

Plus 4 others

for a total of 6

x o

o

o

o o

x

O

S

O

o *

x o

o o

. .

x

o o

-2

o o

. .

. .

O

x x

. .

. .

o o

O

o o

O

S

O

o o

. .

. .

. .

. .

O

. .

x = Sulfur electrons

o = Oxygen electrons

slide41

VSEPR: Valence Shell Electron Pair Repulsion:

A way to predict the shapes of molecules

Pairs of valence electrons want to get as far

away from each other as possible in

3-dimensional space.

slide42

Balloon Analogy for the MutualRepulsion of Electron Groups

Two

Three Four Five Six

Number of Electron Groups

slide45

AX2 Geometry - Linear

..

..

..

..

Molecular Geometry =

Linear Arrangement

..

..

Cl

Be

Cl

BeCl2

1800

Gaseous beryllium chloride is an example of a molecule in which the

central atom - Be does not have an octet of electrons, and is electron

deficient.

Other alkaline earth elements also have the same valence electron

configuration, and the same geometry for molecules of this type.

Therefore this geometry is common to group II elements.

..

..

..

..

O

C

O

CO2

1800

Carbon dioxide also has the same geometry, and is a linear molecule,

but in this case, the bonds between the carbon and oxygens are double

bonds.

slide46

The Two

Molecular

Shapes of the

Trigonal Planar

Electron-Group

Arrangement

slide47

S

O

O

AX3 Geometry - Trigonal Planar

..

..

..

..

All of the boron Family(IIIA)

elements have the same

geometry. Trigonal Planar !

..

..

F

F

BF3

B

Boron Trifluoride

1200

..

..

..

F

AX2E SO2

..

-

..

..

..

..

O

..

..

NO3-

1200

..

..

N

..

..

..

..

O

O

The AX2E molecules have a pair of

Electrons where the third atom

would appear in the space around the

central atom, in the trigonal planar

geometry.

1200

Nitrate Anion

slide48

The Three

Molecular Shapes

of the Tetrahedral

Electron-Group

Arrangement

slide49

107.30

..

N

N

H

H

H

AX4 Geometry - Tetrahedral

H

Methane

H

109.50

CH4

H

C

H

C

H

H

H

H

All molecules or ions with four electron groups around a central atom

adopt the tetrahedral arrangement

H

H

109.50

109.50

+

H+

H

Ammonia is in a tetrahedral shape,

but it has only an electron pair in

one location, so the smaller angle!

all angles are

the same!

Ammonium Ion

H

slide50

The Four Molecular

Shapes of the Trigonal

Bipyramidal Electron-

Group Arrangement

slide51

AX5 Geometry - Trigonal Bipyramidal

..

..

..

..

..

..

F

I

..

..

..

86.20

..

..

..

I

1800

Br

..

F

..

..

..

..

..

I

..

F

..

AX3E2 - BrF3

..

AX2E3 - I3-

..

..

..

Cl

..

..

Cl

..

..

P

Cl

..

AX5 - PCl5

..

..

..

..

..

Cl

..

Cl

slide52

The Three Molecular

Shapes of the

Octahedral

Electron-Group

Arrangement

slide53

AX6 Geometry - Octahedral

..

..

..

..

..

..

..

..

..

..

F

..

F

..

..

..

F

..

F

..

..

..

F

F

..

..

..

..

S

I

..

..

..

..

..

..

F

F

..

..

F

F

..

..

..

..

F

AX5E

Iodine Pentafluoride

AX6

Sulfur Hexafluoride

..

..

..

..

..

..

F

..

F

..

Xe

..

..

..

..

..

F

..

F

Xenon Tetrafluoride

Square planar shape

slide54

Using VSEPR Theory to Determine Molecular Shape

1) Write the Lewis structure from the molecular formula to see the

relative placement of atoms and the number of electron groups.

2) Assign an electron-group arrangement by counting all electron

groups around the central atom, bonding plus nonbonding.

3) Predict the ideal bond angle from the electron-group arrangement

and the direction of any deviation caused by the lone pairs or double

bonds.

4) Draw and name the molecular shape by counting bonding groups

and non-bonding groups separately.