1. Oxidation & Reduction

2. Oxidation The loss of electrons Forms positive ions (cations) The atom that experiences a loss of electrons is called the reducing agent

3. Reduction The gain of electrons Forms negative ions (anions) The atom that experiences a gain of electrons is called the oxidizing agent

4. Redox Oxidation and reduction are paired events occurring as two separate half- reactions In order to have a source of electrons one element must experience oxidation The “free” electrons are taken in by another element that is reduced

5. Oxidation Numbers The terms oxidation and reduction refer to the oxidation number assigned to a particular element This number indicates how many electrons an atom has gained (-) or lost (+) Example: Ca 2+ and O 2-

6. Ca —>Ca 2+ + 2e- (oxidation half-rxn) O + + 2e- —> O 2- (reduction half-rxn) Ca + O —> Ca 2+ + O 2- (net reaction) Ca 2+ and O 2- are ionically bonded to each other via the redox reaction