Oxidation & Reduction

Oxidation The loss of electrons Forms positive ions (cations) The atom that experiences a loss

of electrons is called the reducing agent

Reduction The gain of electrons Forms negative ions (anions) The atom that experiences a gain

of electrons is called the oxidizing agent

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

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: Ca2+ and O2-

Ca —>Ca2+ + 2e- (oxidation half-rxn) O + + 2e- —> O2- (reduction half-rxn) Ca + O —> Ca2+ + O2- (net reaction) Ca2+ and O2- are ionically bonded to

each other via the redox reaction