posted by Alexis .
a redox reaction is a reaction in which
1.only reduction occurs
2.only oxidation occurs
3.reduction&oxidation occur at the same time
4.reduction occurs first and then oxidation occurs
i think its 3 or 4.
It's 3. If something gains electrons it must gain them from somewhere. And that somewhere is losing electrons at the same time. Intermediates may be involved and some of them may be charged; however, I would shy away from 4 because if reduction occurs first followed by oxdn, why couldn't oxdn occur first followed by redn?