Answer : The electrons are gained and the oxidation number of chromium decreases.
Explanation :
As we know that a redox reaction is a reaction in which the oxidation and reduction takes place simultaneously.
Oxidation reaction : The reaction where a substance looses its electrons. In this, oxidation state of an element increases. Or we can say that in oxidation, the loss of electrons takes place.
Reduction reaction : The reaction in which a substance gains electrons. In this, oxidation state of an element decreases. Or we can say that in reduction, the gain of electrons takes place.
The balanced half reaction will be :
[tex]Cr^{3+}+e^-\rightarrow Cr^{2+}[/tex]
In this reaction, the oxidation number of 'Cr' changes from (+3) to (+2) that means 'Cr' gains 1 electron and it shows reduction or the oxidation number decreases.
Hence, the electrons are gained and the oxidation number of chromium decreases.
