You have to remember why atoms/ions undergo oxidation or reduction. It is to achieve an octet state (a noble gas state) because it is stable. Your answer, Na+ has the electronic configuration 1s22s22p6 or [Ne]. Therefore, it is stable.
That's oversimplified.
If you have atoms and ions alone in vacuum, any Na
+ meeting a lone electron will immediately make an Na atom, releasing much energy. Lone ions are not stable. You won't meet them alone at room temperature.
Ions exist (...with some heavy interpretation needed!) in solids and in solutions, only where one or rather several ions of opposite charge, or atoms with partial charge, are immediate neighbours of the ion. Then, the electron movement that creates these "ions" is extremely short, far less than an atom's size, and gets energetically possible.
So when telling "ion" one should know whether in a solid, a plasma, or in a solvent and which one.