F. Schifano, Department of Science
Bayonne High School
Bayonne, NJ 07002
• Five Days of Instruction and Practice
• Two Labs: Covalent vs. Ionic and Molecular Modeling (total 5 points)
• One Day of In-class Review: 16 March 2011
• Afterschool Session: 16 March 2011 3-5 pm
• Full-Unit Test: 17 March 2011 (13.5 points)
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NJCCCS 5.2.12.B.1. (...chemical bonds are the
interactions between atoms that hold them
together in molecules or between oppositely
charged ions.)
Explain how and why chemical bonds form
Distinguish between the types of chemical bond
Relate bond types to observable chemical properties
Indicate the three-dimensional structure of molecules

A chemical bond is a relationship between
two or more atoms that involves the transfer
or sharing of electrons.

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Chemical reactions are the observable
consequences of making and breaking bonds.
The formation or breaking of a bond results
in a chemical change– an energy change and
the production of a new product substance.


Enthalpy is the potential energy stored in
chemical bonds.
Chemical reactions release or absorb heat
because the total enthalpy in the reactants is
different than the total enthalpy of the
products.

Mixtures are combinations of atoms that
involve only physical jumbling rather than
chemical bonding.
◦ Formed and separated by physical changes

Intermolecular forces– weak, transient
interactions between molecules control some
physical, but not chemical properties.
◦ Next unit we will focus on these.


Atoms form bonds because in doing so they
can rearrange their electrons in a way that
makes them more stable.
Bonds are a way for atoms to achieve valence
= 8.
◦ Hydrogen is stable at VAL=0 or VAL =2
◦ Boron is stable at VAL = 6

Gilbert Lewis (ENG-1916) invented the
structures to show on paper how molecules
were bonded.


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Lines represent covalent bonds. Each line
counts as two electrons.
Dots represent unshared electrons.
Unshared pairs are called lone pairs.

Atoms have different needs to achieve
stability so they will form different numbers
and kinds of bonds.
Elements
Valence
Number of
Bonds
Number of
Lone Pairs
Satisfied at
this valence:
H
1
1
0
1
F, Cl, Br, I
7
1
3
8
O, S, Se
6
2
2
8
N, P
5
3
1
8
C, Si
4
4
0
8
B
3
3
0
6
You should copy
this slide to your
formula sheet.
Write the highest
bond order atom
in center
Link together all
other high
bond-order
elements
Resolve all
remaining bonds
so all VAL are
fulfilled





Write the highest bond order element in the
center.
Attach all other high-bond order elements to
this central atom by single bonds.
Show all missing bonds as empty lines.
Use any available 1-bond order elements to
fill up empty bonds.
If there are any empty bonds on adjacent
molecules, use multiple bonds to fill them.

Write the Lewis structures of each of the
following substances.
C
H
CH4
H3CCl
CO2
BF3
HCl
NH3
CH2O
NH2CH3
H2O
H2S
CH3CH2OH
PCl3
N2
H2C2
C
H
CH4
H3CCl
CO2
BF3
HCl
NH3
CH2O
NH2CH3
H2 O
H2 S
CH3CH2OH PCl3
H2 N2
CH2F2