1. Naming ions We classify ions as
Cations – those that have a positive charge
Anions – those that have negative charges
The name of a positive ion is the same as the name of the element
i.e. sodium forms sodium ions, for example
The name of a negative ion is determined by adding “ide” to the stem of the name
i.e. oxygen forms oxide ions and phosphorus forms phosphide ions

2. Polyatomic ions
Polyatomic ions are a group of elements acting as one and will take on one charge acting as one ion (Read Section 5.9)
Example: Nitrate Ion, NO3-, Ionic Charge of -1
Example Ammonium, NH4+, +1

3. Formulas and charges of common Polyatomic ions
Name of polyatomic ion
Ion formula
Ionic Charge
Nitrate ion
NO3-
- 1
Nitrite ion
NO2-
Hydroxide ion
OH-
Hydrogen carbonate ion (also called bicarbonate ion)
HCO3-
Chlorate ion
ClO3-
Carbonate ion
CO32-
- 2
Sulfate ion
SO42-
Phosphate ion
PO43-
- 3
ammonium
NH4+
+ 1

4. Naming compounds involving polyatomic ions
Always use the list of polyatomic ions. To help you.
This will be provided on the exam.
Name the compound of NA2CO3
Sodium Carbonate
Name the compound of Fe(NO3)3
iron (III) Nitrate

5. Writing formulas involving polyatomic ions
What is the chemical formula of sodium phosphate?
Na3PO4
What is the chemical formula of copper(II) nitrate
Cu(NO3)2
For extra practice, complete p. 205 questions 1, 2, 5, 6