Metals - Reactivity series

The reactivity series is an arrangement of metals in order of their decreasing reactivity, determined by their tendency to lose electrons and form positive ions ($M \rightarrow M^{n+} + ne^-$).

The standard order (from most to least reactive) is: Potassium ($K$), Sodium ($Na$), Calcium ($Ca$), Magnesium ($Mg$), Aluminium ($Al$), Carbon ($C$), Zinc ($Zn$), Iron ($Fe$), Hydrogen ($H$), Copper ($Cu$), Silver ($Ag$), and Gold ($Au$).

Metals above hydrogen in the series react with dilute acids (such as $HCl$ or $H_2SO_4$) to produce a metal salt and hydrogen gas ($H_2$).

Highly reactive metals ($K$, $Na$, $Ca$) react vigorously with cold water to produce a metal hydroxide ($MOH$ or $M(OH)_2$) and hydrogen gas ($H_2$).

Metals like Magnesium ($Mg$) react slowly with cold water but vigorously with steam to produce a metal oxide ($MgO$) and $H_2$.

In a displacement reaction, a more reactive metal will displace a less reactive metal from its aqueous salt solution, e.g., $Mg(s) + CuSO_4(aq) \rightarrow MgSO_4(aq) + Cu(s)$.

The method of extraction depends on reactivity: metals above Carbon are extracted via electrolysis of molten ores, while metals below Carbon are extracted by reduction using Carbon or Carbon Monoxide ($CO$).

Thermal stability of compounds increases with the reactivity of the metal. For example, carbonates of reactive metals like $K$ and $Na$ do not decompose upon heating, while $CuCO_3$ decomposes easily into $CuO$ and $CO_2$.