Answer : Half reaction is defined as the reaction which will be <span>either the oxidation or reduction </span>reaction<span> of particular species in a given redox </span>reaction<span>.
So as per the definition in the reaction of,
</span>

<span>
</span>

<span>
here on left and right side </span>

will get cancelled.
and we will get,

Here,

...this is oxidation reaction as Ba is getting reduced to

by losing 2 electrons.
whereas,on the other hand,

...this is reduction reaction as

is getting reduced to Zn by gaining 2 electrons.
What are the answer choices?
Answer: I'm pretty sure it's D
Explanation :I hope
The person whose work led to a periodic table based on increasing atomic number was Henry Moseley.