Naming Ionic
Compounds
Polyatomic Ions (p.224)
• Oxyanion:
• Oxy = oxygen
• Anion= negative ion (nonmetal)
• Naming:
1. Start with the root of nonmetal
2. Add either:
• -ite for fewer oxygen
• -ate for more oxygen (it ate more
oxygen)
LARGER SUBSCRIPT ATE MORE
OXYGEN!
Common Polyatomic Ions
Ion
Name
Ion
Name
NH4
Ammonium *
IO4-
Periodate
NO2-
Nitrite
C2H3O2-
Acetate *
NO3-
Nitrate
H2PO4-
Dihydrogen phosphate
HSO4-
Hydrogen sulfate
CO32-
Carbonate
OH-
Hydroxide *
SO32-
Sulfite
CN-
Cyanide *
SO42-
Sulfate
MnO4-
Permanganate
S2O32-
Thiosulfate *
HCO3-
Hydrogen
carbonate
O22-
Peroxide*
ClO-
Hypochlorite
CrO42-
Chromate
ClO2-
Chlorite
Cr2O72-
Dichromate
ClO3-
Chlorate
HPO42-
Hydrogen phosphate
ClO4-
Perchlorate
PO43-
Phosphate
BrO3-
Bromate
AsO43-
Arsenate
IO3-
Iodate
Naming Polyatomic Ions
NO2 vs. NO3
1st Element = nitrogen
root is nitr
• NO2 = nitr – ite (less oxygen)
• NO3 = nitr – ate (more oxygen)
SO3 vs. SO4
Nonmetal = sulfur
root is sulf
• SO3 = sulf – ite (less oxygen)
• SO4 = sulf – ate (more oxygen)
Polyatomic Ions: 7A Group
Only applies to:
F, Cl, Br, I
Instead of just 2 ions; each have 4!
7A
7A Group
4 oxygen atoms:
per + nonmetal root + ate
3 oxygen atoms:
nonmetal root + ate
2 oxygen atoms:
nonmetal root + ite
1 oxygen atom:
hypo + nonmetal root + ite
Example: Chlorine
• ClO4
: perchlorate
• ClO3
: chlorate
• ClO2
: chlorite
• ClO
: hypochlorite
Naming Compounds: NaCl
1. Write the name of the Metal/Cation(+)
2. The root of the Nonmetal/Anion + ide
Sodium Chlor + ide
Naming: Li2O
Ignore subscript unless
it’s a transition metal
1. Name the Metal/Cation (+)
2. Name the root of the Nonmetal/
Anion
3. Add “ide” to the end
Lithium
Ox + ide
Determining Chemical Formula
•
Refresh: how do you determine an elements oxidation
number?
1. Write down metal’s symbol
oxidation number above)
(with
2. Write down nonmetal’s symbol
(with oxidation number above)
3. Cross your charges to find the
number of atoms (subscripts do not have a
charge and you do not cross “1”).
Examples
1. Potassium Iodide
1+
1-
Don’t cross 1’s
K I
2. Magnesium Bromide
2+
1-
Mg Br 2
Remember: no charge on subscript
TRANSITION
METALS
Naming compounds with
transition metals
• Transition metals have
multiple oxidation numbers
• To determine the charge you
uncross your subscripts
Finding the Charge: Fe2O3
• 1. Cross the subscripts to the top:
Fe2O3

2. Metal is positive: Nonmetal is negative
3+
2-
Fe2O3
Transition Metals
•
Step 1: Cross your subscripts up
Fe2O3
Fe23+O32•
•
Remember: metals are (+) and
nonmetals are (-)
Step 2: Write down the name of the metal followed by parenthesis. Put the charge (not
the subscript) of the metal as a roman numeral in parenthesis.
iron ( ) III
oxide
Step 3: Add the root of the nonmetal + ide
Determining the Formula
Copper (II) Chloride (7A)
Step 1: Write down the metal’s symbol with it’s charge
2+
Cu Cl
1-
Step 2: Write down the nonmetal’s symbol with it’s charge
2+
1-
Cu Cl
2
Step 3: Cross your charges to subscripts (do not keep the +/-)