IONIC COMPOUNDS
Naming and Formula Writing
 OBJECTIVES:
Apply the rules for naming
and writing formulas for
binary ionic compounds.
Apply the rules for naming
and writing formulas for
compounds containing
polyatomic ions.
Predicting Charges on Monatomic Ions
KNOW THESE !!!!
+1 +2
-3 -2 -1
Cd+2
0
Naming Positive Ions
 Before you name an Ion you have to
know the charge.
 Group 1 = always +1
 Group 2 = always +2
 Aluminum = always +3
 Zinc and Cadmium = always +2
 Silver = always +1
The Other Metals
 All other metals can have various positive
charges from +1 to +7
 Roman Numerals are used to tell the
charge
Monatomic Ions
Naming Postive Ions
 With group 1, 2, Al, Zn, Cd, and Ag you
just give the name of the atom




Na+ is Sodium
Mg+2 is Magnesium
Ag+ is Silver
Al+3 is Aluminum
All the other metals
 With all other metals you give the name
Metal followed by a roman numeral





Cu+ - Copper (I)
Cu+2 – Copper (II)
Fe+2 – Iron (II)
Fe+3 – Iron (III)
U+6 – Uranium (VI)
Naming negative ions
 All negative ions have their endings
changed to –ide
 Oxygen becomes oxide
 Fluorine becomes Fluoride
 Nitrogen becomes Nitride
 Chlorine becomes Chloride
Names of other Negative
Ions
 Carbide = what you want your parents to do for
you
 Boride = what happened at the rodeo
 Silicide = what you are seeing right now
 Fluoride = a state in the union
 Iodide = Very sad, I guess we will have to
Barium.
 Telleride = Telling the driver where you want to
go
Formulas of Ionic
Compounds
Formulas of ionic compounds are determined
from the charges on the ions
atoms
Na  +

ions

F : 

sodium + fluorine
Charge balance:

Na+
–
: F :  NaF

sodium fluoride
1+
1-
formula
= 0
Writing a Formula
Write the formula for the ionic compound that will
form between Ba2+ and Cl.
To cancel out Ba’s +2, then two -1 Cl’s are needed.
Solution:
1. Balance charge with + and – ions
2. Write the positive ion of metal first, and the
negative ion
Ba2+ Cl Cl
3. Write the number of ions needed as
subscripts
BaCl2
Balancing a formula by
math
 Every ionic compound should have a
formula that has a charge that equals
zero.
 Barium Fluoride




Ba+2 FHow many F’s are needed to balance Ba+2 ?
Two
Formula is BaF2
Another way – Drop, Swap,
Reduce







Aluminum Oxide
Al is always +3
Oxide is always -2
Al+3, O-2
DROP: Al3O2
SWAP: Al2O3
REDUCE: 2 and 3 are lowest integers,
so leave alone
Another example







Magnesium Oxide
Mg is +2
Oxide is -2
Mg+2, O-2
DROP: Mg2O2
SWAP: Mg2O2
REDUCE: MgO, 2 and 2 divide each
other out.
 Barium phosphide
 Barium will form Ba2+
 Phosphorus will form P3 Formula is Ba3P2
 Sodium sulfide
 Sodium will form Na+
 Sulfur will form S2 Formula is Na2S
 Calcium chloride
 Calcium will form
Ca2+
 Chlorine will form
Cl1 Formula is CaCl2
Complete in your journal
Learning Check
Write the correct formula for the
compounds containing the following
ions:
1. Na+, S2a) NaS
b) Na2S
c) NaS2
2. Al3+, Cla) AlCl3
b) AlCl
c) Al3Cl
3. Mg2+, N3a) MgN
b) Mg2N3
c) Mg3N2
Naming Compounds
Binary Ionic Compounds:
 1. Cation first, then anion
 2. Monatomic cation = name of the element
 Ca2+ = calcium ion
 3. Monatomic anion = root + -ide
 Cl = chloride
 CaCl2 = calcium chloride
Naming Binary Ionic
Compounds
 Examples:
NaCl
 sodium chloride
ZnI2
 zinc iodide
Al2O3
 aluminum oxide
Complete in your journal
Learning Check
Complete the names of the following binary
compounds:
Na3N
sodium
________________
KBr
potassium ________________
Al2O3
aluminum ________________
MgS
_________________________
Transition Metals
Elements that can have more than one possible
charge MUST have a Roman Numeral to indicate
the charge on the individual ion.
1+ or 2+
2+ or 3+
Cu+, Cu2+
copper(I) ion
copper (II) ion
Fe2+, Fe3+
iron(II) ion
iron(III) ion
Names of Variable Ions
These elements REQUIRE Roman Numerals because they can
have more than one possible charge:
anything except Group 1A, 2A, Ag, Zn, Cd, and Al
(You should already know the charges on these!)
Or another way to say it is: Transition metals and the metals in groups 4A and
5A (except Ag, Zn, Cd, and Al) require a Roman Numeral.
FeCl3
CuCl
SnF4
PbCl2
Fe2S3
(Fe3+) iron (III) chloride
(Cu+ ) copper (I) chloride
(Sn4+) tin (IV) fluoride
(Pb2+) lead (II) chloride
(Fe3+) iron (III) sulfide
Examples of Older Names of Cations formed
from Transition Metals
(you do not have to memorize these)
Complete in your journal
Learning Check
Complete the names of the following binary
compounds with variable metal ions:
FeBr2
iron (_____) bromide
CuCl
copper (_____) chloride
SnO2
___(_____ ) ______________
Fe2O3
________________________
Hg2S
________________________
Polyatomic Ions
 Some ions are composed of more then
one atom.
 These are called polyatomic ions
 Poly = more
Formulas and names
 Nitrate = NO3 Sulfate = SO4-2
 Silver nitrate
 Ag+ NO3 DSR = AgNO3
 Copper (I) Sulfate
 Cu+ SO4-2
 Cu2SO4
More Polyatomics
 Lead (IV) Phosphate
 Pb+4 PO4-3
 Pb3(PO4)4
 Notice: When more then one Polyatomic
is present you surround it with ()
 Big: The subscripts on Polyatomic ions
are NEVER changed.
Complete in your journal
Learning Check
Write the correct formula for the compounds
containing the following ions:
1. Na+, PO4-3
a) NaPO4
b) Na2PO4 c) Na3PO4
2. Al3+, NO3a) Al(NO3)3 b) AlNO3 c) Al3NO3
3. NH4+, N3a) NH4N
b) NH4N c) (NH4)3N
Polyatomic Ions you have to
know
NAME
Acetate
FORMULA
C2H3O-1
Carbonate
Chlorate
CO3-2
ClO3-1
Cyanide
Hydroxide
CN-1
OH-1
Nitrate
NO3-1
Peroxide
O2-2
Phosphate
PO4-3
Sulfate
SO4-2
Ammonium
NH4+1
More on Polyatomics
 Most polyatomic ions end in –ate.
 The ending –ite means one less oxygen
is present then in the ending –ate.
 Example: Nitrate versus Nitrite:

NO3NO2 NOTICE: Only the number of O’s
changed, not the charge.
Even More
 The Prefix Hypo means two less oxygen’s are
present then in –ate.

Example: Hyposulfite: SO2-2
 The Prefix Per- means one extra oxygen is
present then in –ate.
 Examples:

Perchlorate
ClO4
Chlorate
ClO3
Chlorite
ClO2
HypoChlorite
ClO-
What if Hydrogen is in it?
 The Prefix Bi means that a Hydrogen is
added, and the charge is reduced by
one.
 Example:
 BiCarbonate
HCO3-1
 May also go by Hydrogen Carbonate.
Practice by writing the
formula or name as
required…
 Iron (II) Phosphate
 Stannous Fluoride
 Potassium Sulfide
 Ammonium Chromate
 MgSO4
Complete in your journal
 FeCl3
Learning Check
Match each set with the correct name:
A.
Na2CO3
1) magnesium sulfite
MgSO3
2) magnesium sulfate
MgSO4
3) sodium carbonate
B.
Ca(HCO3)2 1) calcium carbonate
CaCO3
2) calcium phosphate
Ca3(PO4)2
3) calcium bicarbonate
Complete in your journal
Learning Check
A. aluminum nitrate
1) AlNO3
2) Al(NO)3 3) Al(NO3)3
B. copper(II) nitrate
1) CuNO3
2) Cu(NO3)2
3) Cu2(NO3)
C. Iron (III) hydroxide
1) FeOH
2) Fe3OH
3) Fe(OH)3
D. Tin(IV) hydroxide
1) Sn(OH)4 2) Sn(OH)2
3) Sn4(OH)
Complete in your journal
Things to look for:
1) If cations have ( ), the number
in parenthesis is their charge.
2) If anions end in -ide they are
probably off the periodic table
(Monoatomic)
3) If anion ends in -ate or –ite,
then it is polyatomic
Write the opposite of what is shown; If name shown, write formula; If formula shown, write
name.
1. aluminum sulfide
11. Na2S
2. barium arsenate
12. K2SO4
3. copper (I) nitride
13. LiF
4. ammonium phosphate
14. Zn(NO3)2
5. lead (IV) nitrate
15. FeCl3
6. lithium oxalate
16. CaCO3
7. calcium bicarbonate
17. AlBr3
8. silver permanganate
18. Mg(NO3)2
9. mercury (I) bromide
19. FeSO4
10.chromium (III) sulfite
20. Pb(NO3)2