Chemistry Ch. 9.2
Naming and Writing Formulas for
Ionic Compounds
Naming Binary Ionic Compounds
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Binary compounds are composed of two
elements and can be either ionic or
molecular.
If you know the formula for a binary ionic
compound, you can write its name.
Place the cation name first, followed by
the anion name.
NaBr is sodium bromide. SrF2 is strontium
flouride.
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CuO is not just copper oxide. Copper can
form 1+ and a 2+ cations. The formula
indicates a 1 to 1 ratio. Since oxygen is
always 2-, the correct name is copper(II)
oxide.
What is the formula for copper(I) oxide?
Cu2O.
Writing Formulas for Binary Ionic
Compounds
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Easy. Write the symbol of the cation and
then the anion. Add whatever subscripts
are needed to balance the charges.
Calcium bromide. Ca2+. Br-.
CaBr2
Use the crisscross method, and then
reduce to the lowest whole number ratio if
necessary.
Compounds with Polyatomic Ions
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Again easy. Write the symbol for the
cation followed by the formula for the
polyatomic ion, and then balance the
charges. Use crisscross method.
Ca2+ (NO3)Ca(NO3)2
Naming Compounds with
Polyatomic Ions
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First, figure out if the compound contains
a polyatomic ion!
If so, then to name the compound, simply
state the cation first and then the
anion…the same as for binary ionic
compounds.
NaClO is sodium hypochlorite.
What is (NH4)2C2O4 ?