1. Polyatomic Ionic Compounds Formula to Name

2. Definition
Polyatomic Ion- more than one atom that together have a charge
Polyatomic Ionic Compound- compound containing at least one polyatomic ion +
Cation -
Polyatomic
Anion
Polyatomic Ionic
Compound 2

3. Common Polyatomic Ions
The Appendix of your book (Page A-2) has the following chart
COMMON POLYATOMIC IONS
Acetate, CH3COO-1 or C2H3O2-1
Ammonium NH4+1
Bromate, BrO3-1
Bromite, BrO2-1
Carbonate, CO3-2
Carbonite, CO2-2
Chlorate, ClO3-1
Chlorite, ClO2-1
Chromate, CrO4-2
Cyanide, CN-1
Dichromate, Cr2O7-2
Dihydrogen phosphate, H2PO4-1
Hydrogen carbonate or bicarbonate, HCO3-1
Hydrogen phosphate or biphosphate, HPO4-2
Hydrogen sulfate or bisulfate, HSO4-1
Hydroxide, OH-1
Hypochlorite, ClO-1
Iodate, IO3-1
Iodite, IO2-1
Nitrate, NO3-1
Nitrite, NO2-1
Oxalate, C2O4-2
Perchlorate, ClO4-1
Permanganate, MnO4-1
Peroxide, O2-2
Phosphate, PO4-3
Phosphite, PO3-3
Silicate, SiO3-1
Sulfate, SO4-2
Sulfite, SO3-2

4. Help Identifying Polyatomic Ions
The only cation (front-half) polyatomic ion is “NH4”
All other polyatomic ions are anions (back-half)
The subscripts within the polyatomic ion is important (it must match exactly with the one on your ion list)
If there are parenthesis, the polyatomic ion is inside (ignore the number outside) 4

5. Practice Identifying Polyatomic Ions
NaNO3
NH4Cl
Ca(OH)2
(NH4)3PO4
K2CO3
Example:
Identify and name the polyatomic ion in each compound

6. Practice Identifying Polyatomic Ions
NaNO3
NH4Cl
Ca(OH)2
(NH4)3PO4
K2CO3
Nitrate
Ammonium
Hydroxide
Ammonium & phosphate
Carbonate
Example:
Identify and name the polyatomic ion in each compound

7. Identifying & Naming Polyatomic Ionic
These compounds have:
More than 2 capital letters (non starting with H)
Contain at least 1 metal & 1 non-metal
To name these compounds:
Write the name of the cation (the metal element name or “Ammonium” for “NH4”)
If the anion is a polyatomic ion, write the polyatomic ion’s name just as it is
If the anion is a single non-metal element, write its name with the suffix “-ide” 7

8. Example #4
NaNO3

9. NaNO3 Example #4 Sodium Nitrate Cation Polyatomic Anion “Sodium”9

10. Example #5
K2SO4

11. K2SO4 Example #5 Potassium sulfate Cation Polyatomic Anion “Potassium”11

12. Example #6
Ca(OH)2

13. Ca(OH)2 Example #6 Calcium hydroxide Cation Polyatomic Anion “Calcium”13

14. Example #7
(NH4)2S

15. (NH4)2S Example #7 Ammonium sulfide Polyatomic Cation Anion “Ammonium”
“sulfur” becomes “sulfide”
Ammonium sulfide 15

16. Write the name for the following compounds
Let’s Practice
Ca(NO3)2
Na3PO4
NH4ClO
K2CO3
Example:
Write the name for the following compounds

17. Write the name for the following compounds
Let’s Practice
Ca(NO3)2
Na3PO4
NH4ClO
K2CO3
Calcium nitrate
Sodium phosphate
Ammonium hypochlorite
Potassium carbonate
Example:
Write the name for the following compounds

18. Polyatomic Ionic Compounds Name to Formula

19. Definition
Polyatomic Ion- more than one atom that together have a charge
Polyatomic Ionic Compound- compound containing at least one polyatomic ion +
Cation -
Polyatomic
Anion
Polyatomic Ionic
Compound

20. Identifying & Naming Polyatomic Ionic
These compounds:
Do not end with “-ide” (except hydroxide & cyanide)
Do not use covalent prefixes
To write these formulas:
Write the symbol & charge of the cation & anion
Add additional cations or anions to have a neutral compound
Use subscripts to show the number of ions
When using subscripts with a polyatomic ion, you must put the polyatomic ion in parenthesis.

21. Example #3
Sodium carbonate

22. Example #3
Na+1
Cation
Sodium carbonate
Polyatomic
Anion
CO3-2

23. Na2CO3 Example #3 Sodium carbonate Cation Polyatomic Anion Na+1
= -1
Polyatomic
Anion
Na+Na+CO32-
= 0
CO3-2
Na2CO3
The subscript “2” is used to show that 2 cations are needed.

24. Example #4
Magnesium nitrate

25. Example #4
Mg+2
Cation
Magnesium nitrate
Polyatomic
Anion
NO3-1

26. Mg(NO3)2 Example #4 Magnesium nitrate Cation Polyatomic Anion Mg+2
= 1
Magnesium nitrate
Mg+2NO3- NO3-
Polyatomic
Anion
= 0
NO3-1
The subscript “2” is used to show that 2 anions are needed.
Mg(NO3)2
Use parenthesis when adding subscripts to polyatomic ions

27. Write the following chemical formulas
Let’s Practice
Sodium nitrate
Calcium chlorate
Potassium sulfite
Calcium hydroxide
Example:
Write the following chemical formulas

28. Write the following chemical formulas
Let’s Practice
Sodium nitrate
Calcium chlorate
Potassium sulfite
Calcium hydroxide
NaNO3
Ca(ClO3)2
K2SO3
Ca(OH)2
Example:
Write the following chemical formulas