Balancing Half Equations: Simple Ionic Equations

Key Concepts

• The terms "half-equation" and "half-reaction" can refer to either an oxidation reaction equation or to a reduction reaction equation.

• The electrons lost by an atom or ion during an oxidation reaction can be treated as a product in the reaction.

• The electrons gained by an atom or ion during a reduction reaction can be treated as a reactant in the reaction.

• When the oxidation or reduction reaction equation is balanced:

1. the number of atoms of each element on the left hand side of the equation must equal the number of atoms of each element on the right hand side of the equation

2. the sum of the charges on the left hand side of the equation must equal the sum of the charges on the right hand side of the equation.

Examples of Writing Half-equations for Ions

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