Step-by-step explanation:
Oxidation in an element occurs when it is losing electrons in the chemical reaction. So it will become more positive in charge.
Reduction occurs when an element gains electrons in the chemical reaction. So it will become more negative in charge.
A good way to remember this is:
OIL RIG= Oxidation Is Losing Reduction Is Gaining
So let's first determine the oxidation number of each element and see how Na & Cl charge in charge to determine if they're being reduced or oxidized.
Na + Cl = NaCl
If we refer to our table, lone elements will always be 0.
0 0
Na + Cl = NaCl
Now we can do the products side where we now have a compound so how did they change now that they're bonded together?
According to our table, group 1 is +1 oxidation number. What about Cl? It has to balance our Na so the overall charge of the compound is neutral (0). So it would be -1.
0 0 +1 -1
Na + Cl = NaCl
Na goes from 0 > +1 where it loses e- > oxidation
Cl goes from 0 > -1 where is gains e- > reduction
So our respective half reactions would be:
Na = NaCl and Cl= NaCl
Its okay if we use the product twice, since it's part of both half reactions.