Synthesis
Objective: write reactants and
products in symbols and words for
synthesis reactions—BOTH simple
synthesis and complex synthesis
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…2 become 1…
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Synthesis
There are two kinds of synthesis
Simple & Complex
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For our examples the following notation will be used:
metal
cation
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nonmetal
anion
Simple Synthesis
REACTANTS:
***two elements
+

PRODUCTS:
***one compound
WHAT HAPPENS:
***the two elements combine
NOTES:
• Remember the list of elements that are diatoms
• Remember the cation comes first
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• Remember to write formulas according to criss cross
EXAMPLE
+
chlorine

sodium
Cl2
sodium chloride
Na
NaCl
Na comes first
diatom
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EXAMPLE
+

aluminum
sulfur
aluminum sulfide
Al
S
Al2S3
Al comes first
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Complex Synthesis
REACTANTS:
***two binary compounds with 1 element common to both
PRODUCTS:
***one compound containing a polyatomic ion
WHAT HAPPENS:
***the common element becomes part of a polyatomic ion
Even though complex synthesis and double displacement
both have 2 compounds on the reactant side-complex
synthesis has binary compounds with a common element
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Complex Synthesis
play movie
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EXAMPLE
magnesium oxide + water 
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EXAMPLE
magnesium oxide + water 
MgO
+ H2O
Oxygen is common to
both binary compounds
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EXAMPLE
magnesium oxide + water 
MgO
+ H2O
magnesium is not in any polyatomic ions
—it is on the left side of the periodic table which
makes it on the left side of the compound
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EXAMPLE
magnesium oxide + water 
MgO
+ H2O
hydrogen and oxygen combine in a polyatomic anion
—hydroxide (OH-)
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EXAMPLE
magnesium oxide + water 
MgO
+ H2O

Mg(OH)2
compound formed is magnesium hydroxide
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Complex Synthesis with
Binary Molecular Compounds
• Remember a Binary Molecular Compound
contains 2 non-metal elements that are
right of the metalloid line. It doesn’t
use valence numbers-it uses the prefix
system.
• When a bmc is on the reactant side it
will form a specific polyatomic ion that
should be crossed with the cation for
the product side.
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Complex Synthesis with
Binary Molecular Compounds
Reactant: bmc
• Product: polyatomic ion
• SO2
• SO3
• N2 O3
• N 2 O5
• P2O3
• P2O5
Smaller # of O in bmc=ite polyatomic ion
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Larger # of O in bmc=ate polyatomic
ion
(criss-cross with cation)
•
•
•
•
•
•
SO3-2
SO4-2
NO2-1
NO3-1
PO3-3
PO4-3
Complex Synthesis with
Binary Molecular Compounds
EXAMPLE
Li2O
+
P2O3
Li
?????
3PO3
--when the binary molecular compound is P2O3 the polyatomic ion is PO3-3
-- criss cross this with the cation lithium.
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Complex Synthesis with
Binary Molecular Compounds
EXAMPLE
H2O
+
N2O5
HNO
????? 3
--when the binary molecular compound is N2O5 the polyatomic ion is NO3-1
-- criss cross this with the cation hydrogen.
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Strengthen
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