The reactivity series is a list of metals which are arranged in order of their reactivity. The most reactive metals are at the top, while the least reactive metals are at the bottom.
When metals react, they lose electrons to form positive ions (cations).
M → M+ + e–
How easily a metal loses electrons is a measure of its reactivity. Therefore, the more easily a metal loses electrons, the higher it is placed in the reactivity series.
Metals at the top of the series oxidise more easily, meaning they lose electrons more readily. In contrast, metals at the bottom of the series are less reactive and are more resistant to oxidation. This means they do not lose electrons easily.
Some metals react with cold water to form a metal hydroxide and hydrogen gas.
Metal + Water → Metal hydroxide + Hydrogen
For example, lithium reacts with cold water to form lithium hydroxide and hydrogen gas.
Lithium + Water → Lithium hydroxide + Hydrogen
2Li (s) + 2H2O (l) → 2LiOH (aq) + H2 (g)
Most metals react with dilute acids, such as HCl, to form a salt and hydrogen.
Metal + Acid → Metal salt + Hydrogen
For example, potassium reacts rapidly with dilute hydrochloric acid to form potassium chloride and hydrogen gas.
Potassium + Hydrochloric acid → Potassium chloride + Hydrogen
2K (s) + 2HCl (aq) → 2KCl (aq) + H2 (g)