Polyatomic Ions
an electrically charged group of two or more
covalently bonded atoms that functions as a
single ion
NH4+
ammonium
OH-
hydroxide
NO3-
nitrate
NO2-
nitrite
CO32-
carbonate
______________
HCO3-
hydrogen carbonate (bicarbonate)
More Polyatomic Ions
Sulfur
SO42-
sulfate
SO32- sulfite
HSO4-
hydrogen sulfate
HSO3-
hydrogen sulfite
Phosphate
phosphite
PO33- ____________
PO43-
phosphate
HPO42-
hydrogen phosphate
_______________________________
H2PO4-
dihydrogen phosphate
Naming Ternary Compounds
Contain at least 3 elements
Name the nonmetals as a polyatomic ion
Examples:
NaNO3
Sodium nitrate
K2SO4
Potassium sulfate
Al(HCO3)3
Aluminum bicarbonate
or aluminum hydrogen
carbonate
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
CaCO3
1) calcium carbonate
2) calcium phosphate
Ca3(PO4)2
3) calcium bicarbonate
Solution
A.
B.
Na2CO3
MgSO3
3) sodium carbonate
1) magnesium sulfite
MgSO4
2) magnesium sulfate
Ca(HCO3)2
3) calcium bicarbonate
CaCO3
1) calcium carbonate
Ca3(PO4)2
2) calcium phosphate
Naming Ternary Ionic
Compounds








NaNO3
CaSO4
CuSO3
(NH4)2O
LiCN
Fe(OH)3
(NH4)2CO3
NiPO4
Ionic Names
Consider the following:
Does it contain a polyatomic ion?
-ide, 2 elements  no
-ate, -ite, 3+ elements  yes
Does it contain a Roman numeral?
Check the table for metals not in
Groups 1 or 2.
No prefixes!
Ionic Names
potassium chloride
K+ Cl-

KCl

Mg(NO3)2

CuCl2
magnesium nitrate
Mg2+ NO3copper(II) chloride
Cu2+ Cl-
Ionic Names
NaBr
sodium bromide
Na2CO3
sodium carbonate
FeCl3
iron(III) chloride
Writing Formulas

Write the positive ion, then write the negative
ion
The charges have to add up to zero
Write the number of ions needed as
subscripts
Put more than one polyatomic ions in
parenthesis
If anion ends in -ate or -ite it is polyatomic

Don’t show charges in the final formula.




Learning Check
A. aluminum nitrate
Al(NO3)3
B. copper(II) nitrate
Cu(NO3)2
C. Iron (III) hydroxide
Fe(OH)3
D. Tin(IV) hydroxide
Sn(OH)4
Write the formulas for
Lithium sulfide
Tin(II) oxide
Tin(IV) oxide
Magnesium fluoride
Copper(II) sulfate Iron(III) phosphide
Gallium nitrate
Iron(III) sulfide
Barium nitrate
Ammonium chloride
ammonium sulfide