Charting Reducing Agents and Oxidizing Agents:

In any Redox equation, at least one particle will gain electrons and at least one particle will lose electrons. (Depending on the products, it is possible for these to be the same particle). This is indicated by a change in the particle's oxidation number from one side of the equation to the other.

The change is shown in a chart like this:

• The top arrow shows the element that gains electrons, (reduction).

  MnO₄⁻ is the oxidizing agent because it contains the element that gains electrons.

• The bottom arrow shows the element that looses electrons, (oxidation).

  H₂SO₃ is the reducing agent because it contains the element that looses electrons.

• The arrows show the electrons gained or lost by one atom of each element.
   
• These two arrows identify the two half-reactions.

 
Showing Electrons Gained and Lost

 

Identifying Electrons Gained and Lost Assignment