Writing and Naming
Chemical Formulas
Six Rules
Are
The Key……..
Rule 1
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The positive ion is always
written first in a chemical
formula.
Remember it is the metals on
the left side of the periodic table
that like to be positive when they
become ions.
Example: Sodium chloride NaCl
 Example: Calcium chloride CaCl2
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Rule 2
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The negative ion is written in the
second “half” of the formula.
Non-metals that have become
negative ions change their name
to ending with (–ide.)
Example: Sodium chloride NaCl
 Example: magnesium oxide MgO
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Rule 3
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Subscripts are used to indicate
how many of each ion are
needed in the formula to create
a neutral compound.
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Reminder neutral means having no
charge value.
Example: sodium chloride NaCl
 Example: calcium flouride CaF2
 Example: aluminum sulfide Al2S3
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Rule 4
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Transition metals are located in the
short columns of the Periodic Table.
Because these metals often can have
more than one possible charge Roman
Numerals are used to indicate the
charge on the metal.
Example: tin IV chloride SnCl4
Example: Chromium VI sulfide CrS3
Rule 5
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Polyatomic ions are located in an
alphabetized list on the back of the
Periodic Table.
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The endings -ate and –ite “mean”
mixed with oxygen!
If a polyatomic ion needs a subscript,
the ion must be put in parentheses.
Example: Aluminum hydroxide Al(OH)3
Example: Calcium acetate Ca(C2H3O2)2
Rule 6
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Two non-metals will sometimes
bond covalently.
Because the charges make “no
sense” Latin prefixes are used to
indicate how many of each
substance are found in the
compound.
 Example: N2O4 Dinitrogen
tetroxide
 Example: triphosphorus hexachloride P3Cl6

Lets Practice! Slide 13
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Please write out the following
formulas.
Check charges you may need to
use subscripts!
 Example: Potassium nitride
 Example: Calcium phosphate
 Example: Ammonium oxide
 Example: Gold III chloride
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Lets Practice! Slide 14
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Please correctly name the
following compounds.
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Don’t worry these formulas all
correctly written with correct
subscripts etc….
Example: SrCO3
Example: Ca(NO3)2
Example: CrO3
Example: N2Cl4
More practice………slide 15
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Example: MnCl6
Example:CCl4
Example: (NH4)2S
Example: K2CrO4
Example: Cr Br6
Example: MgC2O4
More practice…………slide 16
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Example: CO2
Example: CaCO3
Example: K2SO4
Example: TiS
Example: Li2SO3
Example: Sr2C
Answers Slide 13
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KNO3
Ca3(PO4)2
(NH4)2O
AuCl3
Answers Slide 14
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SO5
V2S5
Na2SO4
Fe2O3
N3S6
AlBr3
Answers Slide 15
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Manganese VI chloride
Monocarbon tetrachloride
Ammonium sulfide
Potassium chromate
Chromium VI bromide
Magnesium oxalate
Answers Slide 16
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Monocarbon dioxide
Calcium carbonate
Potassium sulfate
Titanium II sulfide
Lithium sulfite
Strontium carbide