Chapter 9-Covalent Bonds

Agenda-Lab - Review - Quiz – Review –Chapter 8 / 9Test – Chapter 8/9

Section 1Why do atoms bond?

To become noble or stableTo achieve an octet (are exceptions)

Covalent Bonds

What is a covalent Bond?

Elements share electrons Majority form between nonmetallic

elements

Result? A Molecule is formed

Covalent Bonds

Lewis DotReview: In your notes draw the following dot structures

and determine the number of bonds for each

H

N

O

C

S

Cl

Ar

Groups and Bonds

Group 15 = 3 BondsPH3

Group 16 = 2 BondsH2S

Group 14 = 4 Bonds

CCl4

Group 17 = 1 BondHCl

Lewis structures

Lewis Dot Structures

It’s a Puzzle… Use the dot structures to make all atoms

octet. Remember… H only has 2 dots and is

never a central atomExample: HCL Draw the dots and put them together

Example: H2S

Lewis Dot Structures

Draw the dots and put them together

Sigma BondThe single covalent bond is calls the…

“Sigma Bond”

Shared electrons between two atoms

Multiple Covalent Bonds

Why Multiple Bonds? Hint: Think Noble. To achieve an Octet!Example: C2H4

Draw the central atoms Attach the surrounding atoms

Make sure each atom has an octet

Sigma and pi Bonds

Sigma Bonds Two atoms share electrons

pi Bonds Parallel orbitals over lap Forms double bonds

Example: C2H4

Let’s take a closer look

Lets take a closer look

Strength and Energy

Bond Strength The shorter the bond length, the stronger the

bond, the greater the bond-dissociation energy

Bond Energy Endothermic – more energy is needed to break

the bond than is released Exothermic – more energy is released during

bond formation than is required to break it.