The activity series of metals is an empirical tool used to predict products in displacement reactions and reactivity of metals with water and acids in replacement reactions and ore extraction. It can be used to predict the products in similar reactions involving a different metal.
The activity series is a chart of metals listed in order of declining relative reactivity. The top metals are more reactive than the metals on the bottom. For example, both magnesium and zinc can react with hydrogen ions to displace H2 from a solution by the reactions:
Mg(s) + 2 H+(aq) → H2(g) + Mg2+(aq)
Zn(s) + 2 H+(aq) → H2(g) + Zn2+(aq)
Both metals react with the hydrogen ions, but magnesium metal can also displace zinc ions in solution by the reaction:
Mg(s) + Zn2+ → Zn(s) + Mg2+
This shows magnesium is more reactive than zinc and both metals are more reactive than hydrogen. This third displacement reaction can be used for any metal that appears lower than itself on the table. The further apart the two metals appear, the more vigorous the reaction. Adding a metal like copper to zinc ions will not displace the zinc since copper appears lower than zinc on the table.
The first five elements are highly reactive metals that will react with cold water, hot water, and steam to form hydrogen gas and hydroxides.
The next four metals (magnesium through chromium) are active metals that will react with hot water or steam to form their oxides and hydrogen gas. All the oxides of these two groups of metals will resist reduction by H2 gas.
The six metals from iron to lead will replace hydrogen from hydrochloric, sulfuric and nitric acids. Their oxides can be reduced by heating with hydrogen gas, carbon and carbon monoxide.
All the metals from lithium to copper will combine readily with oxygen to form their oxides. The last five metals are found free in nature with little oxides. Their oxides form through alternate pathways and will readily decompose with heat.
This series chart works remarkably well for reactions that occur at or near room temperatures and in aqueous solutions.
Activity Series of Metals
|Lithium||Li||displaces H2 gas from water, steam and acids and forms hydroxides|
|Magnesium||Mg||displaces H2 gas from steam and acids and forms hydroxides|
|Iron||Fe||displaces H2 gas from acids only and forms hydroxides|
|Hydrogen gas||H2||included for comparison|
|Antimony||Sb||combines with O2 to form oxides and cannot displace H2|
|Mercury||Hg||found free in nature, oxides decompose with heating|