Notes:Color Guide
• Gold: Important concept. Write this down.
• Orange: Definition. Write this down.
• Blue: Important information, but you do not
need to copy.
• Red: Example. Copy if needed.
• White: General Discussion (Don’t Copy)
Chapter 6: Chemical Reactions
Section 1: Forming Compounds
• Definition: chemical reaction – the process
that causes a substance to change into a new
substance.
– Chemical reactions cause atoms to REARRANGE.
– One example of a chemical reaction occurs when cations
join with anions.
Chemical
Reaction
Ionic compounds form when cations and
anions bond together.
• When ionic compounds form, the new
compound must have no charge.
In other words, all of the + and - charges must
cancel out.
Charged
Charged
Neutral!
Each cation and anion has it’s own charge. Lets look
at the cations first. Please copy into your notes.
Use only the element symbols.
Group 1
1+ Charge
Group 2
2+ Charge
Group 13
3+ Charge
Lithium: Li1+
Beryllium: Be2+
Aluminum: Al3+
Sodium: Na1+
Magnesium: Mg2+
Potassium: K1+
Calcium: Ca2+
Rubidium: Rb1+
Strontium: Sr2+
Cesium: Cs1+
Barium: Ba2+
Francium: Fr1+
Radium: Ra2+
And now for the anions:
• When a nonmetal becomes an anion, it’s name changes.
– Example: Fluorine  Fluoride
– Example: Oxygen  Oxide
Group 17
1- Charge
Fluoride: F1-
Group 16
2- Charge
Oxide: O2-
Group 15
3- Charge
Nitride: N3-
Chloride: Cl1-
Sulfide: S2-
Phosphide: P3-
Bromide: Br1-
Selenium: Se2-
Iodide: I1Astatine: At1-
In order to form the new compound, the anions and
cations must cancel each other’s charg.
What happens if the charges DON’T cancel out???
• To make Sodium Oxide, there must be enough
Sodium Cations to balance the Oxygen Anion.
Why don’t we add another sodium
cation to the reaction?
Na1+
Na1+
O2-
Na2O1
It took 2 Sodium
to balance the 1 Oxide.
• Lets try another one. How about Magnesium
Chloride?
Mg2+
Cl1Cl1-
Mg1Cl2
It took 2 Chloride
to balance the 1 Magnesium.
• This stuff is actually pretty easy…
Try these on your own:
•Aluminum Bromide
AlBr3
•Calcium Nitride
Ca3N2
One more thing to remember…the metal always
comes first. It keeps its original name.
The nonmetal comes second. It changes it’s name.
Easy!
• Covalent compounds are named based on the
number of atoms they contain.
1
2
3
4
5
6
7
8
– Prefixes are used to represent the number of atoms.
The Prefixes Are:
Rules:
Mono
•If the first element has only one
Di
atom, it gets no prefix.
Tri
•The first element uses it’s original
Tetra
name.
Penta
Hexa
Hepta
Octa
Examples:
• Carbon Di-oxide 
• Di-Hydrogen Di-oxide 
• Sulfur Tetra-Chloride 
Chapter 6: Chemical Reactions
Section 2: The Nature of Chemical Reactions
There are often signs that a chemical reaction is
taking place:
– Color Change
– Gas Production (bubbling)
– Energy Transfer (getting hot or cold, glowing)
– These signs indicate that something is being
changed & new substances are forming.
So, in a chemical reaction…things REACT to PRODUCE other things.
• Definition: reactants – the substances in a
chemical reaction that are changed.
• Definition: products - the NEW substances
produced in a chemical reaction.
– The product must contain the same elements as
the reactant.
Hydrogen
C8H18 + O2
Carbon
Hydrogen
Carbon
Oxygen
H2O + CO2
Oxygen
During a chemical reaction, atoms are rearranged.
Lets look at the reaction of gasoline and oxygen again…
– It would be far to dangerous to use gasoline as a
fuel if it immediately reacted with oxygen, right?
– What do we need in order to start the reaction?
A SPARK!
• Some chemical reactions need energy in
order to begin.
– Energy breaks the atomic bonds and allows the
atoms to rearrange.
– Once the bonds are broken, the reactants
rearrange into the products.
Perhaps the most important rule in chemistry
is:
• Definition: Law of Conservation of Mass – states
that “In a chemical reaction, mass is never
created or destroyed.”
– In other words, you MUST have the same number of
atoms in the reactant as you have in the product.
Some reactions release energy as they occur…
– Definition: exothermic change – a physical
or chemical change that releases energy.
•Exo. changes make the air warmer or give off
light (or both).
•Examples: combustion and condensation
Some reactions absorb energy as they
occur…
–Definition: endothermic change – a
physical or chemical change that
absorbs energy.
•Endo reactions lower the temp.
•Examples: evaporation
Chapter 6:
Chemical Reactions
Section 3: Types of Reactions
• Definition: chemical equation – a
representation of a chemical reaction using
element symbols.
– The  means “yields” or “produces”.
Chemical reactions are classified based on what
happens to the reactants.
Some reactions break the reactants apart…
Others causes them to join together.
Others just make them change places.
• When things combine together in a chemical
reaction, we call it “synthesis”.
• Definition: synthesis reaction – a reaction in
which two or more substances combine.
• The general formula is:
–A + B  AB
• A and B represent the reactants…
• AB represents the product.
When a chemical reaction breaks substances apart, it
is called “decomposition”.
• Definition: decomposition reaction – a
reaction in which a compound breaks
down into simpler substances.
The general formula is:
AB A+B
• AB represents the reactant.
• A + B represent the products.
In replacement reactions, substances
change places.
• Definition: single replacement reaction – a
reaction in which one element takes place of
another to form a new compound.
–The general formula is:
–AX + B  BX + A
– Definition: Double Replacement reaction –
a reaction in which two elements trade
places.
–The general formula is:
–AX + BY  AY + BX
Notice that X takes the place of Y
and Y takes the place of X.
• Definition: combustion reaction – an exothermic
reaction in which oxygen is (usually) a reactant.
– Combustion reactions often produce H2O and CO2 as
products.