As Sn undergoes removal of 4 electrons in this reaction, it is termed as oxidation reaction.
Explanation:
Chemical reactions can be further classified as oxidation and reduction reaction. As chemical reactions consists of transfer of electrons from one element to another, it leads to formation of oxidation and reduction reaction. It is known that if an element releases electrons to attain stable state, then that element is said to undergo oxidation reaction. Similarly, if an element accepts electrons to attain stable state , then it is termed as reduction reaction.
In the present case, the reactant side contains Sn element in 2+ ionized state or oxidized state as 2 electrons are already removed in this state. And in the product side, the oxidation number increased to +4 . This means more 2 electrons are released from Sn in the product side. So as Sn undergoes removal of 4 electrons in this reaction, it is termed as oxidation reaction.
