I II III IV

Ch. 8 - Covalent Bonding

I. The Covalent Bond(p. 240 – 247)

A. Why Do Atoms Bond?

Gain stabilityLower potential energyAtoms that fulfill the octet rule are more

stable

balanced attraction & repulsion

increased repulsion

attraction vs. repulsion

B. What is a covalent bond?

A chemical bond that results from the sharing of electrons

Molecule = two or more atoms

that are held together by

covalent bondsMajority of covalent bonds form between

nonmetals (CLOSE together on periodic table)

H2O

Examples:

Which of the following are covalent compounds?

NaBr SiO2

CO2

AlCl3 CH4

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

Properties Table

Physical State solid liquid or gas

odorousForm electrolytes in

solution

C. Covalent Bonding Formation

Diatomic molecule = molecule containing only two atoms

Some atoms exist this way because they are more stable than the individual atoms Cl2

N O F

Cl

Br

I

H

D. Diatomic Elements

The Seven Diatomic Elements

Br2 I2 N2 Cl2 H2 O2 F2

E. Lewis Structures

Electron Dot Diagrams show valence e- as dots distribute dots like arrows

in an orbital diagram 4 sides = 1 s-orbital, 3 p-orbitals EX: oxygen

2s 2pO

X

E. Lewis Structures

Octet Rule Most atoms form bonds in order to obtain 8 valence

e-

Full energy level stability ~ Noble Gases

Ne

E. Lewis Structures

Example Electron Dot Notations:

Ca

P

H

C

CaP

E. Lewis Structures

Single Bonds When atoms share one pair of electrons The two shared electrons belong to both

atoms simultaneously Lewis Structure dots or a line symbolize a

single covalent bond (1 pair of shared e-)

H – H

How would you draw the Lewis structure for fluorine?

Diatomic!

F – F

E. Lewis Structures

E. Lewis Structures

Multiple Covalent Bonds When atoms share more

than one pair of electrons Have higher bond energies

and are shorter than single bonds

E. Lewis Structures

Double Bonds Sharing two pairs of

electrons between two atoms

Draw Lewis Structures for 2 oxygen atoms

E. Lewis Structures

Triple Bonds Sharing three pairs of

electrons between two atoms

Draw Lewis Structures for 2 nitrogen atoms

I II III IV

Naming Molecules

Section 8.2

C. Molecular Nomenclature

Prefix System (binary compounds)

1. Less e-neg atom comes first.

2. Add prefixes to indicate # of atoms. Omit mono- prefix on first element.

3. Change the ending of the second element to -ide.

PREFIXmono-di-tri-tetra-penta-hexa-hepta-octa-nona-deca-

NUMBER12345678910

C. Molecular Nomenclature

CCl4

N2O

SF6

carbon tetrachloride

dinitrogen monoxide

sulfur hexafluoride

C. Molecular Nomenclature

arsenic trichloride

dinitrogen pentoxide

tetraphosphorus decoxide

AsCl3

N2O5

P4O10

C. Molecular Nomenclature

+ -

+

B. Lewis Structures

Nonpolar Covalent - no charges

Polar Covalent - partial charges