Bonding with Chemistry

Lewis Dot Structures

VSEPR and Molecular Geometry

A chemical bond is made by sharing electrons between two atoms to achieve the outer electron configuration of the noble gases.

Chemical Bonds

Ionic Covalent

Polar (dipole moment)

Nonpolar

Each element has a preferred outer shell electron configuration.

An element tends to form enough bonds to achieve the number of electrons corresponding to the nearest noble gas.

This is a periodic (repeating) property of each column (family) of elements.

So the number of outer shell electrons can be determined from the periodic table:

1 H

2 He

3 Li

4 Be

5 B

6 C

7 N

8 O

9 F

10Ne

11Na

12Mg

13Al

14Si

15P

16S

17Cl

18Ar

19K

20Ca

21Sc

22Ti

23V

24Cr

25Mn

26Fe

27Co

28Ni

29Cu

30Zn

31Ga

32Ge

33As

34Se

35Br

36Kr

37Rb

38Sr

39Y

40Zr

41Nb

42Mo

43Tc

44Ru

45Rh

46Pd

47Ag

48Cd

49In

50Sn

51Sb

52Te

53I

54Xe

55Cs

56Ba

57La**

72Hf

73Ta

74W

75Re

76Os

77Ir

78Pt

79Au

80Hg

81Tl

82Pb

83Bi

84Po

85At

86Rn

87Fr

88Ra

89Ac**

104Rf

105Ha

106Sg

107Ns

108Hs

109Mt

110 111 Etc.

Lewis dot structures provide a simple means to determine bonding capacity:

Bonding requirements for achieving an octet of electrons in the outer orbital:

Element Bonds needed

C 4

N 3

P 3 or 5

O 2

S 2 or 6

F 1

Cl 1

Br 1

I 1

H 1

VSEPR = valence shell electron pair repulsion theory indicates what molecular geometry we expect.

Essential bonding characteristic of carbon atoms:

Carbon has 4 outer shell electrons.It needs 4 more to achieve the Neon

configuration of 1s22s22p6.It forms 4 bonds total.

Never forget this. It will help you a lot!!!

Review:

How many bonds does hydrogen form? How many bonds does oxygen form? How many bonds does carbon form?

What is the molecular geometry of water? What is the molecular geometry of oxygen

gas? What is the molecular geometry of CH4?

Organic chemistry

We begin with Hydrocarbons

Hydrocarbons are composed of the elements __________ and __________, just like the name implies.

Three major classes of hydrocarbons Alkanes Alkenes Alkynes

Speaking of alkanes, alkenes, alkynes, etc:

Every subject has its own language. Listen to military people talk and you know this is true!

Organic chemistry is positively loaded with new language to learn. Hang in there, it will come with time…

Alkanesaka saturated hydrocarbons

StructureNames = nomenclatureProperties

PhysicalChemical

We don’t have to stop at C10… for example, C20 is called eicosane. We’ll see that in a later chapter.

# Carbons Name1 methane2 ethane3 propane4 butane5 pentane6 hexane7 heptane8 octane9 nonane10 decane

Counting the organic way

Melting and boiling points of alkanes

Straight Chain Alkanes: Melting Points (o C)

-182

-183

-188

-138 -1

30

-95

-91

-57

-54

-30 -26 -1

0 -5.5 6 10

18 22 28 32 36.8

-200

-150

-100

-50

0

50

0 5 10 15 20

Number of carbon atoms

Me

ltin

g p

oin

t (o

C)

Straight Chain Alkanes: Boiling points (o C)

-161

.5

-88.

6 -42.

1 -0.5 36

.1 68.7 98

.4 125.

7 174.

1

195.

9

216.

3

235.

5

253.

5

270.

5

287 30

3

316.

7

330

343

150.

8

-200

-100

0

100

200

300

400

0 5 10 15 20

Number of carbon atoms

Bo

ilin

g p

oin

t (o

C)

Cycloalkanes

Structural featuresNomenclatureProperties: similar to noncyclic alkanes

Alkenesaka unsaturated hydrocarbons

Structural featuresNomenclatureProperties

PhysicalChemical

Melting and boiling points of alkenes

Alkenes: Melting points (o C)

-169

-185 -185

-139

-106

-165

-138 -140

-119

-200

-180

-160

-140

-120

-100

-80

-60

-40

-20

0

0 1 2 3 4 5 6 7 8

Number of carbon atoms

Mel

tin

g p

oin

t (o

C)

Alkenes: Boiling points (o C)

-151

-47

30

63

94

31

0.93.7

-6.3

-200

-150

-100

-50

0

50

100

150

0 1 2 3 4 5 6 7 8

Number of carbon atoms

Bo

ilin

g p

oin

t (o

C)

Alkynesaka unsaturated hydrocarbons

Structural featuresNomenclatureProperties

PhysicalChemical

More families of organic compounds:

When we introduce other atoms than carbon and

hydrogen into hydrocarbons, we call these

functional groups. They have their own special

names.

Examples of functional groups:

C C OH

CH3

CH3

CH3

CH3

H3CH3C

CH3

OH

O

OH

Cl

Cl

Cl

O

OH

ibuprofen

O

H

11

12

More examples of functional groups in molecules:

O

O

O

OH

OH

HO

O

O

O

N

HO

O

O

OH

erythromycin

Review:

Chemical bonding re: carbon compounds How many bonds?

Three major classes of hydrocarbons 1. 2. 3.

Counting the organic way:

Recognizing functional groups

Problems to practice on:

Chapter 11 & Chapter 12: check out the chapter problems sheet for recommended problems for practice.