Matt
Parts of the Atom
Chemical Reaction Basics
 What
part of the atoms are
affected?
Figure: Valence Electrons
 Electrons (valence electrons) are
affected in reactions because
they decide how reactive is the
atom.
 An atom with one valence
electron is more reactive than an
atom with seven valence
electrons (Figure)
 Eight is the most valence
electrons in an atom.
▪ These atoms are not reactive.
 Electrons are lost or gained in
chemical reactions.
▪ Oxidized: Atom loses electrons
▪ Reduced: Atom gains electrons
Gray atom has 1 valence electron
Green atom has 7 valence electrons
http://www.visionlearning.com/library/module_viewer.php?mid=54
Volume Library 1 Chapter 7 page 17 Oxidation-reduction reaction
Events during Chemical Rx
Chemical Reaction Basics

What is happening during a chemical reaction?
 Bonds between atoms or molecules have interactions among their
electrons breaking and/or forming new bonds.
http://wiki.answers.com/Q/What_happens_when_a_chemical_reaction_occurs
Description
Reference
Reactants & Products
Application of Law of
Conservation of Mass
Reactants which are the
substances that go into the
reaction come out as final
substances called products
No matter what you do to
the substance in chemical
reactions it will still have the
same mass.
Actually law: Matter cannot be
created nor destroyed only
rearranged.
http://www.nelsonthornes.com/secon
dary/science/scinet/scinet/reaction/ch
ange/reactant.htm
http://en.wikipedia.org/wiki/Conservat
ion_of_mass
Five Signs of a
Chemical Rx
Five signs:
 Change of color
 Formation of gas
 Formation of precipitate
(solid separates for a
solution)
 Change of temperature
 Energy produced
http://wiki.answers.com/Q/What_are_
the_5_signs_of_a_chemical_reaction
Role of Energy in Chemical Rx

Forms of Energy
 Potential Energy– substances have a energy due to electrons and bonds. This is the energy that bonds already have to start with for a
reaction.
 Activation Energy– threshold energy needed to initiate a chemical Rx or energy requirement to have a chemical reactions. This is the
hump need to get over. (On next slide)

Types of Energy Reactions (Table)
Exothermic Rx
Endothermic Rx
Description
Chemical reactions that release energy as
part of their product
Chemical reactions that absorb energy to form the
product
Basic Concept
A + B  AB + energy
A + B + energy  AB
Example
Combustion of methane
CH4 + 2O2  CO2 + 2H2O
Sports “Cold pack”
2NH4NO3(5) + H2O(1) + heat  NH4+(aq) + NO3–(aq)
Graphic
1.http://www.kentchemistry.com/links/Kinetics/PEDiagrams.htm
2. http://genchem.chem.wisc.edu/demonstrations/Images/06thermo/methanebubbles.jpg
3. http://dopamine.chem.umn.edu/chempedia/index.php/Cold_Packs/Hot_Packs

Exothermic reaction
 Graphic illustrates that a
chemical reaction (x-axis)
occurs when a threshold energy
is achieved (“activation energy”)
and a product is formed that
generates heat (ΔH along yaxis)

Endothermic reaction
 Figure depicts much energy is
needed (y-axis) to “activate” the
reaction (x-axis)
 Products of this reaction make
surrounding area colder due to
higher energy needs to activate
the reaction
http://www.kentchemistry.com/links/Kinetics/PEDiagrams.htm
Types of Chemical Reactions
Synthesis
Decomposition
Combustion
Single
Replacement
Double
Replacement
Description
Two substances
combine to make a
single product
One substance is
broken down into
two substances
Oxygen is a reactant
and products include
carbon dioxide &
water
One element
replaces another as
part of a compound
Two compounds
“switch partners”
Basic
Concept
A + B  AB
AB  A + B
CxHy + O2  CO2 +
H20
A + BC  AB + C
AB + YZ  AY + BZ
Example
Iron and sulfur
yields iron (II)
sulfide
Electrolysis of water
to make oxygen and
hydrogen gas
Burning of
naphthalene
Magnesium replaces
hydrogen in water to
yield magnesium
hydroxide and hydrogen
gas
Lead (II) nitrate with
potassium iodide
forms lead (II) iodide
and potassium nitrate
http://farm3.static.flickr.com/2110/
1508159256_cde784b80b.jpg?v=
0
http://img.sparknotes.com/figures/0/
02480ae8fc1a41b131a3fdb5a698e9
a3/lyticcell.gif
http://www.separationsnow.com/FCK
editor/UserFiles/Image/sepNOW_ezin
es_2006/0601_sfcdetector1.jpg
http://chem200.tripod.com/flame2.gif
http://www.nitrogenorder.org/experim
ent/dblreplace.shtml
8 Fe + S8  8 FeS
2 H2 O  2 H2 + O 2
C10H8 + 12 O2 
10 CO2 + 4 H20
Mg + 2 H20 
Mg(OH) 2 + H2
Pb(NO3)2 + 2 KI 
PbI2 + 2 KNO3
Chemical
Formula
Video on Chemical Reactions
http://misterguch.brinkster.net/6typesofchemicalrxn.html
Bibliography
 Parts of the Atom
http://www.visionlearning.com/library/module_viewer.php?mid=54 Volume Library 1 Chapter 7 page 17 Oxidation-
reduction reactions
 Events during chemical reaction
wiki.answers.com/Q/What_happens_when_a_chemical_reaction_occurs
http://www.nelsonthornes.com/secondary/science/scinet/scinet/reaction/change/reactant.htm
http://en.wikipedia.org/wiki/Conservation_of_mass
http://wiki.answers.com/Q/What_are_the_5_signs_of_a_chemical_reaction
 Role of Energy in Chemical Reactions
http://www.kentchemistry.com/links/Kinetics/PEDiagrams.htm
http://genchem.chem.wisc.edu/demonstrations/Images/06thermo/methanebubbles.jpg
http://dopamine.chem.umn.edu/chempedia/index.php/Cold_Packs/Hot_Packs
 Energy and Chemical Reactions
 Types of Chemical Reactions
http://www.kentchemistry.com/links/Kinetics/PEDiagrams.htm
http://misterguch.brinkster.net/6typesofchemicalrxn.html