what os necessary for a non metal to be reduced
Nonmetals also have high electron affinity. This means that it is energetically favorable to add an electron to a nonmetal. So, nonmetals can be easily reduced. Metals tend to have low electron affinity so it is more difficult to add electrons (or reduce them). In short: Metals have low ionization energies and low electron affinities so they are readily oxidized. Nonmetals have high ionization energies and high electron affinities so they are readily reduced.