# 8.13.2.5: Oxidizing Ability of the Group 17 Elements

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Consider a reaction between one halogen—​chlorine, for example—and the ions of another—iodide, in this case. The iodide ions are dissolved from a salt such as sodium iodide or potassium iodide. The sodium or potassium ions are spectator ions and therefore irrelevant to the reaction, which proceeds as follows:

$Cl_2 + 2I^- \rightarrow 2Cl^- + I_2 \nonumber$

• The iodide ions lose electrons to form iodine molecules; they are oxidized.
• The chlorine molecules gain electrons to form chloride ions. They are reduced.

This is a redox reaction in which chlorine is acting as an oxidizing agent. The driving force force this reaction is straightforward to identify from the table of Standard Reduction Potentials (Table P2).