the species oxidized shows a(n) the species oxidized shows a(n) drop zone empty. the species reduced shows a(n) the species reduced shows a(n) drop zone empty. the species that shows a decrease in oxidation number is the the species that shows a decrease in oxidation number is the drop zone empty. the species that shows an increase in oxidation number is the the species that shows an increase in oxidation number is the drop zone empty. reducing agent. decrease in oxidation number. oxidizing agent.