Remember this---> LEO= lose electons oxidation... and GER----> gain electrons reduction
so if you look for the one being oxidized, it is the one losing electrons. since electrons are negative, when an atom lose them, it becomes less negative, so more positive.
you can identify the oxidization when the atom becomes more positive.
so in the given reaction: <span>Ni + Sn4+ → Ni2+ + Sn2+ </span> Ni becomes Ni +2 and Sn+4 becomes Sn+2
as you can see the Ni become Ni+2 so more positive
