Naming Compounds Having
Polyatomic Ions
Objective: To learn the names of
common polyatomic ions and how to
use them in naming compounds.
Define polyatomic ion
• A group of atoms with a charge
• Some Examples
• SO42CNC2H3O2• sulfate
cyanide
acetate
• OHNO3NO2• Hydroxide nitrate
nitrite
Polyatomic vs. Monatomic
• How are the ions S2- and SO42- different?
• SO42- is five atoms combined to make one
ion.
• SO43- is a polyatomic ion
Turn to page 100
• Note the table listing the most common
polyatomic ions.
• This table will be supplied to you when
you take the test.
• Let’s look at it.
What do you notice about the
names of most polyatomic ions?
• Most end with either –ite or –ate.
• Notice there are some that end in -ide.
• Perchlorate ClO4• chlorate ClO3• chlorite ClO2• hypochlorite ClO• Chloride
Cl-
Naming Compounds that Contain
Polyatomic Ions
• Say the name of the positive ion
• Say the name of the negative ion
• Na2SO3
K2SO4
• sodium sulfite
potassium sulfate
• KC2H3O2
• Potassium acetate
This will be easier if you remember
this:
• Compounds only have two names
• CuCO3
• Copper(II) carbonate
Compounds Containing SO42• The name of the polyatomic ion is sulfate
• BaSO4
Al2(SO4)3
• barium sulfate
aluminum sulfate
• CaSO4
• calcium sulfate
Na2SO4
sodium sulfate
Compounds Containing OH• The name of the polyatomic ion is hydroxide
• NaOH
Cu(OH)2
• sodium hydroxide
copper(II) hydroxide
• Al(OH)3
Fe(OH)2
• aluminum hydroxide Iron(II) hydroxide
Compounds Containing C2H3O2• Ba(C2H3O2)2
• Barium acetate
Cu(C2H3O2)2
copper(II) acetate
• Mg(C2H3O2)2
• Magnesium acetate
Hg2(C2H3O2)2
mercury(I) acetate
Compounds Containing H2PO4The name of the polyatomic ion is
dihydrogen phosphate.
• NaH2PO4
• Remember: Say the name of the positive
ion and then the name of the negative
ion.
• Sodium dihydrogen phosphate
Writing Formulas of Compounds
that Contain Polyatomic Ions
• Sodium phosphate
Write the Formula for
Barium Nitrate
• Barium
Nitrate
Write the Formula for
Calcium Hydroxide
• Calcium
Hydroxide
Write the Formula for
Calcium chloride
• Only put parentheses around polyatomic
ions
Write the formula for ammonium
carbonate
• ammonium
carbonate