Reactivity of metals Metals typically have positive valency. For example sodium has a valency of one. Aluminum has a valency of 3 and so on. Metals therefore, form cations or tend to donate electrons to the electrons to the atoms to which they bond. The rate at which a metal will react with water, oxygen or acids depends on the metal's ability to release Valence electrons. Therefore, metals react at different rates. For example , sodium and potassium react with water very rapidly. Because of this, they are stored under oil to prevent direct contact with water and oxygen slowly. On the basis of this, metals are classified into two groups. These are Reactive metals Non reactive metals