Ionic Compounds-Polyatomic Ions

A group of atoms that form a unit that stays together but has an overall charge. Each polyatomic ion has its own
name, formula and charge. Treat each ion as one entity, do not separate atoms!
Ex. (NO3)-1  contains one nitrogen, three oxygen's, has an overall charge of -1 and is called nitrate.
Common Polyatomic Ions and their Charges
Name
Ammonium
Nitrate
Nitrite
Hydroxide
Bicarbonate (hydrogen
carbonate)
Carbonate
Chlorate
Sulfate
Phosphate
Ion Formula
(NH4)+1
(NO3)-1
(NO2)-1
(OH)-1
(HCO3)-1
Charge
+1
-1
-1
-1
-1
(CO3)-2
(ClO3)-1
(SO4)-2
(PO4)-3
-2
-1
-2
-3
Naming Compounds Involving Polyatomic Ions
1. Write the name of the most metallic element and leave it unchanged, check to see if it is multivalent.
2. If it is multivalent, reverse the criss-cross rule to get the roman numeral and write it down
3. Write the name of the polyatomic ion second and leave it unchanged
Na(NO3)
Ca3(PO4)2
Al(ClO3)3
Cu(OH)2
Sn(SO4)
Ni(NH4)3
Writing formulas for compounds with Polyatomic Compounds
Follow the same steps as you did for writing the formula of an ionic compound. Be aware of multivalent transition
metals.
Copper II nitrate
Tin II carbonate
Magnesium nitrite
Aluminum phosphate
Lithium sulfate
Strontium hydroxide