This document discusses polyatomic ions and writing formulas for ionic compounds containing polyatomic ions. It defines polyatomic ions as groups of atoms with an overall ionic charge. Common polyatomic ions such as ammonium, hydroxide, nitrate, and phosphate are presented. The document provides examples of writing formulas for ionic compounds using polyatomic ions by balancing charges between cations and anions. It also discusses naming ionic compounds containing polyatomic ions by writing the name of the metal cation first followed by the polyatomic ion.

1. IONIC COMPOUND WITH
POLYATOMIC IONS

2. Polyatomic Ions
A polyatomic ion is a group of atoms with an overall ionic charge.
NH4
+ ammonium OH− hydroxide
NO3
− nitrate NO2
− nitrite
CO3
2− carbonate PO4
3− phosphate
HCO3
− hydrogen carbonate (or bicarbonate)

3. Polyatomic Ions

4. Naming Polyatomic Ions
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5. Names and Formulas of Common
Polyatomic Ions

6. Names and Formulas of Common
Polyatomic Ions

7. Writing Formulas for
Compounds with
Polyatomic Ions
To write the correct formula for compounds
containing polyatomic ions, first determine the
ratio of ions using charge balance.
Write the formula for calcium nitrate.
1. The total negative and positive charges must
equal zero

8. Writing Formulas for Compounds with
Polyatomic Ions
2. When more than one polyatomic ion is needed for charge balance, the subscript is written
outside the closing parenthesis of the polyatomic ion.
Ca2+ + 2 NO3
−  Ca(NO3)2
Calcium ion + 2 Nitrate ions Calcium nitrate

9. Guide to
Writing
Formulas with
Polyatomic
Ions

10. Learning
Check
Write the formula for aluminum
bicarbonate.

11. Solution
Write the formula for aluminum bicarbonate.
Step 1 Identify the cation and polyatomic
ion (anion).
Cation Polyatomic Ion (anion)
Al3+ HCO3
−

12. Solution
Write the formula for aluminum bicarbonate.
Step 2 Balance the charges.

13. Solution
Write the formula for aluminum bicarbonate.
Step 3 Write the formula, cation first, using the subscripts
from the charge balance.
Al3+ + 3 HCO3
−  Al(HCO3)3
Aluminum + 3 Bicarbonate ions Aluminum bicarbonate

14. Naming Ionic
Compounds with
Polyatomic Ions
When naming ionic compounds containing polyatomic ions,
• write the name of the positive ion, usually a metal first
• write the name of the polyatomic ion last
Learn to recognize polyatomic ions in ionic compound names and
formulas.

15. Naming Ionic Compounds with
Polyatomic Ions

16. Guide to Naming
Ionic
Compounds with
Polyatomic Ions

17. Learning Check
Name the following ionic compounds:
A. KClO3
B. Mn(OH)2

18. Solution
Name the following ionic compounds:
A. KClO3
B. Mn(OH)2

19. Summary of
Naming Ionic
Compounds

20. Learning Check
Name the following ionic compounds.
A. Na3P
B. CuSO4
C. Cr(ClO)3

21. Solution
Name the following ionic compounds.
A. Na3P
B. CuSO4
C. Cr(ClO)3