1. Writing a formula for an Ionic Compound:
1st Write the symbols for the ions side by side
(cation first):
2nd Cross over the charges :
Al+3 O-2
3rd Check the subscripts (the smallest
possible ratio of ions):
Al+3
O-2
Al2O3
Al2O3

2. Practice:
K+1 Br
Mg+2 Cl
Na+1 O
Mg+2 O
K+1 (NO3 )
Na+1 (SO4 )
Pb+2 (NO3 )
Al+3 (SO4 )
KBr
MgCl2
Na2O
Mg2O2
MgO
KNO3
Na2SO4
Pb (NO3)2
Al2(SO4)3

3. Writing names of ionic compounds:
Write the name of the cation followed
by the name of the anion:
cation
anion
Element’s name
Monatomic
Polyatomic
The suffix of the element name change by ide.
See reference table
(SO4 ) sulfate.
(NO3 ) nitrate.
Chlorine
Chloride
(NO2 ) nitrite.
Oxygen
Oxide

4. Examples:
MgCl2
Magnesium chloride
Na3PO4
Sodium phosphate
CaO
Calcium oxide
BaSO4
Barium sulfate

5. Writing names of ionic compounds:
If the cation has more than one
oxidation number, you must write it
between parenthesis (using roman
numeral):
Examples:
Fe2O3
Iron (III) oxide
CuCl
Copper (I) chloride

6. Practice:
Write the name of the following:
LiBr
AlF
MgO
Ba(OH)
Na2CO
Cu(NO3)
FeCl
NiSO
Na3N
Lithium bromide
Aluminum fluoride
Magnesium oxide
Barium hydroxide
Sodium carbonate
Copper (II) nitrate
Iron (III) chloride
Nickel (II) sulfate
Sodium nitride