Unit 5B
Nomenclature:
Ionic Compounds
(Part 1)
What’s an ionic compund?
•When a metal + a
nonmetal combine
Naming Ionic compounds
1.Positive cation
(metal) written
st
1
2.Negative anion
(nonmetal) is
nd
written 2
+
Na
Cl
Naming Ionic compounds
3. Keep the first name
the same
4. Change the ending of
the second to –ide
Sodium + Chlorine 
Sodium Chloride
+
Na
Cl
Practice Problems
1. NaBr
• Sodium Bromide
2. KF
• Potassium Flouride
3. MgI2
• Magnesium Iodide
4. Rb2O
• Rubidium Oxide
5. Li3N
• Lithium Nitride
6. Ag2S
• Silver Sulfide
Writing ionic
formulas
Ionic formulas are called:
Formula Units
Review of Charges
+4/-4
+1
+2
+3
TRANSITION
METALS
-3 -2 -1
0
Criss-Cross Method
K+S
1. Write the (+) ion first and the (-)
ion second
+
2-
K +S
2. Criss-cross the charges and write
them as subscripts. Get rid of the
charges
K2S
3. Reduce if necessary
Examples
Li + Cl
+1
-1
Mg + Cl
+2
-1
C+O
+4
-2
Li + Cl
Mg + Cl
C+O
Li1 +Cl1
Mg + Cl
C+O
MgCl2
CO2
LiCl
1
2
2
4
Examples
Potassium chloride
+
K

Cl
KCl
Magnesium sulfide
2+
Mg
2S
Lithium oxide
1+
2Li O
 MgS

Li2O
Unit 5B
Nomenclature:
Ionic Compounds
(Part 2)
Polyatomic Ions
• group of covalently bonded atoms that have a
charge (poly = many)
• Examples:
SO4 2-
SO3 2-
ClO3-
ClO2-
Sulfate
Sulfite
Chlorate
Chlorite
• Most end with an –ite or –ate suffix
• Most have a negative charge (except NH4+)
Naming Polyatomic Ions
• Rules are the same as naming ionic
compounds, with one exception
– First name stays the same
– Polyatomic ion has its own name (use chart)
• Examples:
–NaOH
–Ca(NO2)2
–Fe2(SO4)2
Sodium Hydroxide
Calcium Nitrite
Iron Sulfate
Writing
formulas
Polyatomic
Ions
Criss-Cross Method
Ca + NO3
1. Write the (+) ion first and the (-)
ion second
+2
1(
)
Ca
NO
3
2. Criss-cross the charges and write them
as subscripts. Get rid of the charges
Ca(NO
)
3
2
3. Use parenthesis if more than
1 polyatomic ion
Practice Problems
Calcium
Hydroxide
Ca2+ OH-
Ca(OH)2
Potassium
Chlorate
+
K
KClO3
Ammonium
Bromide
NH4+ Br-
Strontium
Nitrate
2+
Sr
1ClO3
NO3
NH4Br
Sr(NO3)2
Unit 5B
Nomenclature:
Ionic Compounds
(Part 3)
Charges
•Charges of SOME atoms can
easily be predicted by their
position on the periodic table.
•Charges of Transition Metals
(Groups 3-12) are more difficult to
predict because they “transition”
between multiple charges
Transition Metals
•When a compound contains a
transition metal, it’s charge is
indicated by a Roman Numeral
•The Roman Numeral is written in
parentheses as part of it’s name
•Example:
Chromium (III) Chloride
Transition Metals
Chromium (III) Chloride
• The roman numeral is the
charge for Cr : Cr3+
•The charge for Cl: Cl-
•What would the formula be?
CrCl3
Practice Problems
Iron(III) Oxide
Fe 3+ O2-
Fe2O3
Tin(IV) Chloride
Sn 4+ Cl-
SnCl4
Copper(II) Bromide Cu 2+ Br-
CuBr2
Mercury(II) Sulfide Hg 2+ S2-
HgS
Now work backwards
Write the name if given the formula
SnF2
Sn2+ F-
Tin(II) Flouride
Pb3N2
Pb2+
Lead(II) Nitride
N3-
MnO2 Mn 4+ O2HgO
2+
Hg
2O
Manganese(IV)
oxide
Mercury(II) oxide