Post on 15-Feb-2016
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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 ON C
Valence ElectronsTell us # e to share
Paired electrons NOT shared
FF
Lewis Structure PracticeH
O
N
C
H ON C
Number of Bonds
H H
O
C
NHH
H HH
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 ON 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
attractionUnits 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