The use of oxidation numbers to identify redox systems

The oxidation number is a hypothetical charge assigned to atoms in molecules and ions using a set of specific rules. Since redox reactions involve transfers of electrons, identification of the atoms which change oxidation number will show the atoms, ions or molecules which are specifically involved in the redox process. 

If the oxidation number of an atom becomes more positive Iduring the reaction, it has lost electrons. . and has been Qx/d/zed. 

Exarrlple If you consider the unbalanced equation for-the reaction shown on p. 53 - 

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