Answer:
![Ni^(2+)](https://img.qammunity.org/2020/formulas/chemistry/college/qfy2wssosvg264x08mxjiu8dprxubdznlq.png)
Step-by-step explanation:
From the equation attached ,
is reduced. This is because reduction is equivalent to decrease in the oxidation number. In the equation , The oxidation number of Ni is reduced from +2 to 0.
NB, The oxidation number of a neutral atom is zero