REACTIVITY SERIES OF METALS/ELEMENTS.
Metals compete for combined Oxygen. A metal/element with higher affinity for oxygen removes Oxygen from a metal lower in the reactivity series/less affinity for Oxygen.
When a metal/element gains/acquire Oxygen, the process is called Oxidation.
When metal/element donate/lose Oxygen, the process is called Reduction.
An element/metal/compound that undergoes Oxidation is called Reducing agent. An element/metal/compound that undergoes Reduction is called Oxidizing agent.