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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