Lesson 1 Oxidation Numbers
Oxidation Numbers: assigned to atoms or ions as a way to keep track of electron transfers *top right corner of PT

Rules for Assigning Oxidation Numbers
1. Free elements are always zero (ex: H2, Na, S8) 
2. Ions are the charge on the ion.  
3. Oxygen: –2 oxidation number
4. Hydrogen: oxidation number of +1 
                         except metal hydrides -1 (Group 1&2 metals)
5. Compounds total zero.
Polyatomic ion equals the charge of the ion (ex: sulfate = -2)