A list in which the metals are arranged in the decreasing order of their chemical reactivity is called the metal reactivity series.
Special features of the activity series:
1. The ease with which a metal in solution loses an electron(s) and forms a positive ion decreases down the series, i.e. from potassium to gold.
2. Hydrogen is included in the activity series because, as metals do, it too loses an electron and becomes positively charged (H +) in most chemical reactions.
3. The series facilitates the comparative study of metals in terms of the degree of their reactivity.
4. The compounds of the metals (oxides, carbonates, nitrates and hydroxides) too can be easily compared.
