Ionic Formulas
What are ions?
• Review: What’s the difference between monatomic and
polyatomic ions?
Monatomic Ion – ion with only
one element
Polyatomic Ion – ion with more
than one element
WARNING!
• We’re going to start out with JUST MONATOMIC
IONS.
• We’ll work on POLYATOMIC IONS later.
Ionic Compound
Ionic Compound – a compound in
which positive and negative ions
attract each other to keep matter
together
- Overall charge of the compound is
neutral
Ionic Formula
• How do we represent an ionic compound?
Ionic Formula – Similar to a
chemical formula, this shows what
ions (AND how many of each ion)
are in an ionic compound
Writing Ion Practice
Look at the ions and formulas listed below. Do you notice
any patterns?
Ions Formula
Li+ FLiF
Na+ ClNaCl
Be2+ O2- BeO
Mg2+ O2- MgO
Al3+ N3- AlN
Ions
Li+
O2Na+ N3Mg2+ FAl3+ ClBe2+ N3-
Formula
Li2O
Na3N
MgF2
AlCl3
Be N
Writing Formulas – Equal Charges
Ions Formula If the cation and anion
charge are the same
Li+ FLiF
value:
Na+ ClNaCl
Drop the charges and
write the elements
Be2+ O2- BeO
Mg2+ O2- MgO
Cation
first,
then
anion
Al3+ N3- AlN
Writing Formulas – Equal Charges
Example 1) Lithium Fluoride
+
Li
F
LiF
Writing Formulas – Equal Charges
Example 2) Magnesium Oxide
2+
Mg
2O
MgO
Writing Formulas – Different
Charges
If the cation and anion
charge are not equal,
1 cation and 1 anion will
not form a neutral
compound.
Ions
Li+
O2Na+ N3Mg2+ FAl3+ ClBe2+ N3-
Formula
Li2O
Na3N
MgF2
AlCl3
Be3N2
Writing Ionic Formulas
STEP
1) Write the cation
first, then the anion.
EXAMPLE
Aluminum Chloride
Al3+ Cl-
Writing Ionic Formulas
STEP
2) Drop the + and –
(but NOT the
numbers!!)
EXAMPLE
Aluminum Chloride
Al3
Cl1
Writing Ionic Formulas
STEP
3) Cross the charges.
EXAMPLE
Aluminum Chloride
Al3
Cl1
Al1Cl3
Writing Ionic Formulas
STEP
4) Drop any “1”.
EXAMPLE
Aluminum Chloride
Al1Cl3
AlCl3
Writing Ionic Formulas
STEP
1) Write the cation
first, then the anion.
EXAMPLE
Beryllium Nitride
Be2+ N3-
Writing Ionic Formulas
STEP
2) Drop the + and –
(but NOT the
numbers!!)
EXAMPLE
Beryllium Nitride
Be2
N3
Writing Ionic Formulas
STEP
3) Cross the charges.
EXAMPLE
Beryllium Nitride
Be2
N3
Be3N2
Writing Ionic Formulas
STEP
4) Drop any “1”.
EXAMPLE
Beryllium Nitride
Be3N2
Be3N2
Writing Ionic Names
Rule: Cation is written as its element’s name.
Anion name ends in –ide.
**Sometimes we have to figure out the name
from the formula.
Given the ionic formula, work backwards to
figure out the ions.
Names – Example 1
CaBr2
Ca2+
Br-
Calcium Bromide
Names – Example 2
CoI3
Co3+
I-
Cobalt (III) Iodide
Names – Example 3
CuS
Must have the same charge:
Cu2+
S2-
Copper (II) Sulfide
Group Practice
• There are 11 stations around the room. Find them all,
and write the ionic formula and name for each in your
notebook.
• You will need to bring your Ion Chart with you, since
some of the ions are written with NAMES, others with
SYMBOLS
Group Practice - Check
Station Cation
1
2
3
4
5
6
7
Anion
K+
O2Na+
BrCa2+
Iodide
Calcium
S2Al3+
Fluoride
Iron (III)
Te2Ag+
P3-
Ionic
Formula
Ionic Name
Group Practice - Check
Station Cation
8
9
10
11
Anion
Ionic
Formula
Li3N
Ga2Se3
Cu2O
CuO
Ionic Name
Group Practice - Check
Station Cation
Anion
1
2
3
4
5
Ionic
Formula
K+
O2K2O
Na+
BrNaBr
Ca2+
Iodide
CaI2
Calcium
S2CaS
Al3+
Fluoride
AlF3
6
7
Iron (III)
Ag+
Te2P3-
Fe2Te3
Ag3P
Ionic Name
Potassium Oxide
Sodium Bromide
Calcium Iodide
Calcium Sulfide
Aluminum
Fluoride
Iron (III) Telluride
Silver Phosphide
Group Practice - Check
Station Cation
Anion
Ionic
Formula
Li+
Ga3+
Cu+
Cu2+
N3Se2O2O2-
Li3N
Ga2Se3
Cu2O
CuO
8
9
10
11
Ionic Name
Lithium Nitride
Gallium Selenide
Copper (I) Oxide
Copper (II) Oxide
Independent Practice
• Fill out the Monatomic Ions Practice