1. Polyatomic Ionic Compounds

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

3. Common Polyatomics Name Symbol OH-1 Hydroxide NO3-1 Nitrate ClO3-1
Chlorate
CO3-2
Carbonate
SO4-2
Sulfate
PO4-3
Phosphate
NO2-1
Nitrite
SO3-1
Sulfite
CN-1
Cyanide
HCO3-1
Bicarbonate
C2H3O2-1
Acetate
ClO4-1
Perchlorate
ClO2-1
Chlorite
ClO-1
Hypochlorite
NH4+1
Ammonium

4. Practice Identifying Polyatomic Ions
NaNO3
NH4Cl
Ca(OH)2
(NH4)3PO4
K2CO3
Example:
Identify and name the polyatomic ion in each compound
Note: Parenthesis are only used on POLY’s and only when we need more than one. You can’t change the subscript on the poly.
Example - Al2(SO4)3 Three SO4-2 groups NOT SO43-2

5. 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

6. Naming Polyatomic Ionic Compounds
To name these compounds:
Write the name of the cation
If it is a metal just name the metal
If it is a multivalent metal, name the metal and put a set of parenthesis after it
If it is a NH4 write down the name ammonium
Name the anion
If the anion is a polyatomic ion, just name the polyatomic
If the anion is a single non-metal element, write its name with the suffix “-ide”
Determine the roman numeral if it is multivalent

7. Example #1
NaNO3

8. NaNO3 Example #1 Sodium Nitrate Cation Polyatomic Anion “Sodium”

9. Example #2
K2SO4

10. K2SO4 Example #2 Potassium sulfate Cation Polyatomic Anion “Potassium”

11. Example #3
Cu(OH)2

12. Cu(OH)2 Example #3 Copper (II) hydroxide Cation Polyatomic Anion
“Copper” A Multivalent Metal
Cation
Two OH-1 groups provide a total charge of -2. The Copper has to be +2 to balance this charge.
Cu(OH)2
Polyatomic
Anion
“hydroxide”
Copper (II) hydroxide

13. Example #4
(NH4)2S

14. (NH4)2S Example #4 Ammonium sulfide Polyatomic Cation Anion “Ammonium”
“sulfur” becomes “sulfide”
Ammonium sulfide

15. Writing Formulas for Polyatomic Ionic
Get out your Poly List!!!!
To write these formulas:
Write the symbol & charge of the cation & anion
Add additional cations or anions to have a neutral compound. (We once again do this by balancing charge. Methods such as the Swap/Drop/Reduce or Lowest Common Multiple)
Use subscripts to show the number of ions
When using subscripts with a polyatomic ion, you must put the polyatomic ion in parenthesis.

16. Example #1
Sodium carbonate

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

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

19. Example #2
Magnesium nitrate

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

21. Mg(NO3)2 Example #2 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