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)