I II III IV

Chemical Bonding

Introduction toBonding

A. Vocabulary

• Chemical Bond

• attractive force between atoms or ions that binds them together as a unit

IONIC COVALENTBond Formation

Type of Structure

Solubility in Water

Electrical Conductivity

OtherProperties

e- are transferred from metal to nonmetal

high

yes (solution or liquid)

yes

e- are shared between two nonmetals

low

no

usually not

MeltingPoint

crystal lattice true molecules

B. Types of Bonds

Physical State solid liquid or gas

odorous

“electron sea”

METALLICBond Formation

Type of Structure

Solubility in Water

Electrical Conductivity

OtherProperties

MeltingPoint

B. Types of Bonds

Physical State

e- are delocalized among metal atoms

very high

yes (any form)

no

malleable, ductile, lustrous

solid

Ionic Bonding - Crystal Lattice

RETURN

B. Types of Bonds

Remember:

Opposites Attract!

Covalent Bonding - True Molecules

RETURN

B. Types of Bonds

Diatomic Molecule

Metallic Bonding - “Electron Sea”

RETURN

B. Types of Bonds

C. Bond Polarity

Difference in electronegativity determines bond type.

Above 1.7 = ionic

0.3-1.7 = polar covalent

0- up to 0.3 = non-polar covalent

C. Bond Polarity

• Polar Covalent Bond

• more e-neg atom has a partial negative charge -

• less e-neg atom has a

partial positive charge +

• Nonpolar Covalent Bond

• e- are shared equally

• usually between identical atoms

• Ex. F2

C. Bond Polarity

• Nonpolar

• Polar

• Ionic

View Bonding Animations.

C. Bond Polarity

C. Bond Polarity

Examples:

Cl2

HCl

NaCl

3.0-3.0=0.0Nonpolar

3.0-2.1=0.9Polar

3.0-0.9=2.1Ionic

D. Lewis Structures

Electron Dot Diagrams show valence e- as dots

EX: oxygen

2s 2pO

X

D. Lewis Structures

Covalent – show sharing of e-

Ionic – show transfer of e-

D. Lewis Structures

Covalent – show sharing of e-

Ionic – show transfer of e-

+ -

+

D. Lewis Structures

Nonpolar Covalent - no charges

Polar Covalent - partial charges

18Steps for Building a Dot Steps for Building a Dot Structure for Structure for Covalent Covalent CompoundsCompounds

Steps for Building a Dot Steps for Building a Dot Structure for Structure for Covalent Covalent CompoundsCompounds

Ammonia, NH3

1. Decide on the central atom; never H. Why?

Most of the time, this is the least electronegative atom

• Therefore, N is central on this one

2. Add up the number of valence electrons that can be used.

H = 1 and N = 5

Total = (3 x 1) + 5

= 8 electrons

NH3

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3.Form a single bond between 3.Form a single bond between the central atom and each the central atom and each surrounding atom (each surrounding atom (each bond takes 2 electrons!)bond takes 2 electrons!)

H H

H

N

Building a Dot StructureBuilding a Dot Structure

H••

H

H

N4. Remaining electrons form 4. Remaining electrons form LONE PAIRS to complete the LONE PAIRS to complete the octetoctet

3 BONDING PAIRS and 1 LONE 3 BONDING PAIRS and 1 LONE PAIR.PAIR.

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5.5. Check to make sure there are 8 Check to make sure there are 8 electrons around each atom electrons around each atom except H. except H.

• H should only have 2 electrons. H should only have 2 electrons.

Building a Dot StructureBuilding a Dot Structure

6. 6. Also, check the number of electrons in Also, check the number of electrons in your drawing with the number of your drawing with the number of electrons from step 2. electrons from step 2.

• If you have more electrons in the drawing If you have more electrons in the drawing than in step 2, you must make double or triple than in step 2, you must make double or triple bonds. bonds.

H••

H

H

N

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Carbon Dioxide, COCarbon Dioxide, CO22Carbon Dioxide, COCarbon Dioxide, CO22

1. Central atom = 1. Central atom =

2. Valence electrons =2. Valence electrons =

3. Form bonds.3. Form bonds.

O OC4. Place lone pairs on outer atoms.4. Place lone pairs on outer atoms.

This leaves 12 electrons (6 pair).This leaves 12 electrons (6 pair).

5. Check to see that all atoms have 8 electrons 5. Check to see that all atoms have 8 electrons around it except for H, which can have 2.around it except for H, which can have 2.

C 4 e-C 4 e-O 6 e- X 2 O’s = 12 e-O 6 e- X 2 O’s = 12 e-Total: 16 valence Total: 16 valence electronselectrons

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Carbon Dioxide, COCarbon Dioxide, CO22Carbon Dioxide, COCarbon Dioxide, CO22

••O OC

•• ••

••••••

••O OC

•• ••

••••••

••O OC

•• ••

••

••O OC

•• ••

••

6. There are too many electrons in our drawing. 6. There are too many electrons in our drawing. We must form DOUBLE BONDS between C and O. We must form DOUBLE BONDS between C and O. Instead of sharing only 1 pair, a double bond Instead of sharing only 1 pair, a double bond shares 2 pairs. So one pair is taken away from shares 2 pairs. So one pair is taken away from each atom and replaced with another bond.each atom and replaced with another bond.

C 4 e-C 4 e-O 6 e- X 2 O’s = 12 e-O 6 e- X 2 O’s = 12 e-Total: 16 valence electronsTotal: 16 valence electrons

How many are in the drawing?How many are in the drawing?

23Double and Double and even triple even triple bonds are bonds are commonly commonly observed for observed for C, N, P, O, and C, N, P, O, and SS

••O OC

•• ••

••

••O OC

•• ••

••

HH22COCO

SOSO33

CC22FF44

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Now You Try One!Now You Try One!Draw Sulfur Dioxide, SODraw Sulfur Dioxide, SO22

Now You Try One!Now You Try One!Draw Sulfur Dioxide, SODraw Sulfur Dioxide, SO22