Ch 9 COVALENT BONDING

Covalent bondsChemical bond that results from the sharing

of

TWO electrons

Covalent bonds

Covalent bonds

Covalent bonds

Covalent BondsBalancing Act of Attractive and Repulsive

Forces

Electrostatic Forces

DiatomicsHydrogenNitrogen OxygenFluorineChlorineBromineIodine

H2

N2

O2

F2

Cl2

Br2

I2

Are you Listening????What is a covalent bond? How is it different

from an Ionic Bond.

Covalent bonds are the chemical bonds formed when atoms SHARE electrons. TCovalent IonicShare electrons transfer electrons

Lewis StructuresAtomic symbol with valence electrons around

it

H H

Lewis Structures1. Find atomic symbol

2. Determine number of valence electron

3. Place electrons alone first

4. Pair up if needed

F7 valence electrons

Lewis Structure PracticeH

O

N

C

H O

N C

Valence ElectronsTell us # e to share

Paired electrons NOT shared

FF

Lewis Structure PracticeH

O

N

C

H O

N C

Number of Bonds

H H

O

C

NHH

H H

H

H

HH H

σ

What is a single covalent bond? Why does it form?

A single covalent bond is the sharing of two electrons by two atoms with each atom contributing one electron to the shared paired.They form to allow atoms to become stable by having access to 8 electrons!!!!

Orbitals and BondingSigma bonds can form between

2s orbitals

1s , 1p

2p

Bonding orbital – region where bonding electrons are likely to be found

Multiple Covalent Bonds

O O

N N

DOUBLE BOND

TRIPLE BOND

Make Me some π

Write this down!!!Why do multiple covalent bonds form?

They form that so that atoms can have access to 8 electrons. In other words so that atoms can obtain a NOBLE GAS CONFIGURATION

Bond LengthDistance between nuclei at the MAX

attraction

Units are usually Å1Å = 10-10 m 1m = 1010 Å

Convert 0.05 m to ÅConvert 1.46 Å to mConvert 2.65 Å to nmConvert 123 pm to Å

5.0*108 Å1.46*10-10 m26.5 nm1.23 Å

Bond Strength

H HO O

N N

Lowest Energy Distance

Distance

ENERGY

Lowest Energy Distance

Distance

ENERGY

Lowest Energy Distance

Distance

ENERGY

Lowest Energy Distance

Distance

ENERGY Bond Dissociation

Energy

Almost DoneF2 1.43 Å

O2 1.21 Å

N2 1.10 Å

159 kJ/mol

498 kJ/mol

945 kJ/mol

How is bond length related to bond dissociation energy?

The shorter the bond the larger the dissociation energy.

EnergyEnergy is always released when making a

chemical bond

Energy is always added when breaking a chemical bond

Need to look at TOTAL ENERGY of a RXN

Endo vs ExoExothermic – energy is

flowing outEndothermic – energy

is flowing into