Redox

REDOX REACTION

A reaction involving the transfer of electrons between atoms, which is identified by a change in oxidation numbers for the species involved.

OXIDATION

The process where a species loses electrons (OIL); the oxidation number becomes more positive (increases)

REDUCTION

The process where a species gains electrons (RIG); the oxidation number becomes more negative (decreases)

OXIDIZING AGENT

The reactant that causes oxidation by itself being reduced (it gains electrons)

REDUCING AGENT

The reactant that causes reduction by itself being oxidized (it loses electrons)

OXIDATION NUMBER (STATE)

The theoretical charge assigned to an atom based on a set of rules, used to track electron transfer; a change indicates a redox reaction

HALF-REACTION METHOD

A systematic method for balancing complex redox reactions by separating the overall process into an oxidation half-reaction and a reduction half-reaction

STANDARD REDOX METHOD

The half-reaction method used when the reaction is in a neutral or unspecified medium (electrons are the only things added to balance charge)

ACIDIC REDOX METHOD

The half-reaction method used when the reaction is in acidic solution; H2O is used to balance O atoms, and H+ is used to balance H atoms

BASIC REDOX METHOD

The half-reaction method used when the reaction is in basic solution; the reaction is balanced as if it were acidic, and then OH- ions are added to both sides to neutralize the H+ ions

OXIDATION NUMBER RULE 1

Elements in their natural, uncombined state always have an oxidation number of zero (Na, O2, Cl2)

OXIDATION NUMBER RULE 2

Monatomic ions have an oxidation number equal to their charge (Fe2+ = 2+)

OXIDATION NUMBER RULE 3

Oxygen almost always has an oxidation number of -2 (except in peroxides, (O2)2-, where it is -1)

OXIDATION NUMBER RULE 4

Hydrogen almost always has an oxidation number of +1 (except in metal hydrides, where it is -1)

OXIDATION NUMBER RULE 5

The sum of the oxidation numbers in a neutral compound must equal zero; the sum in a polyatomic ion must equal the charge of the ion