Reactivity series is the series of metals based on their reactivity from highest to lowest. So, reactivity series of metals can be defined as a series of metals, in order of reactivity from highest to lowest. It is also known as activity series. The reactivity of metals is because of their incomplete outer orbitals or due to their electronic configuration. Metals form positively charged ions as they tend to lose electrons. Metals with high atomic numbers tend to be more reactive as their electrons are far from the positively charged nucleus. So, they can be removed easily.
Metals from potassium to calcium are highly reactive and even react with water. While metals from magnesium to lead can react with acids. Metals from copper to platinum are highly unreactive and don’t react with any other substance in normal conditions. This is the reason why platinum and gold don’t get corrode easily and don’t form oxides. While metals such as zinc, aluminum, magnesium, calcium etc. form oxides readily.
Hydrogen is a non-metal but still it has been included in the reactivity series as it helps in the comparison of reactivity of metals.
Metals present at the top of reactivity series are highly electropositive metals. The electropositive character of metals decreases as we go down the series.
Reducing power of metals decreases as we go down the series. Thus, potassium is the strongest reducing agent.
As we go down the reactivity series, the ability of metals to remove hydrogen from hydrides decreases.
Metals present in the reactivity series above hydrogen can remove hydrogen ions from dilute HCl or Dilute sulphuric acid.
The metal which is more reactive than other metal can remove less reactive metal from its salt. Thus, metals placed at the top of the reactivity series can remove the metals which are present at the bottom of the series from their salts.
The metals which are placed above in the series can be extracted by electrolysis. While metals from Zinc to Hg can be extracted by simply reducing their oxides, which is an inexpensive method.
When we move down the series the electron-donating capacity of metals decreases.
In displacement reaction – Displacement reactions are those reactions in which more reactive metal displaces less reactive metal from its salt. So, by reactivity series you can tell which metal will displace another metal.
Reaction between metals and water – Metals from potassium to calcium can react with cold water and release hydrogen gas.
Chemical Equations for the reaction of K and Ca with cold water are:
K (s) + H2O (l) → KOH (aq) + ½ H2 (g)
Potassium Cold Water Potassium Hydroxide Hydrogen
Note: Potassium reacts extremely violently with water to form a colorless aqueous solution of KOH with a release of12mole of H2 gas. The resultant solution is basic because of the dissolved hydroxide.
Ca + H2O (l) → Ca(OH)2 (aq) + ½ H2 (g)
Calcium Cold Water Calcium Hydroxide Hydrogen
Note: Ca virtually remains unreactive with cold water; however, it forms calcium hydroxide with a release of half mole of H2 gas.
Reaction between metals and acids – Lead and other metals which are more reactive than lead in the reactivity series can react with hydrochloric acid and sulphuric acid and form salts. Thus, we can predict the reactions by reactivity series.
Chemical Equations for the reaction of Pb with HCl and HSO4 to form salts are:
Pb (s) + 2HCl (aq) → PbCl2 (aq) + H2 (g)
Lead Hydrochloric Acid Lead Chloride Hydrogen
Note: Pb reacts slowly with acids like HCl and HNO3 and releases bubbles of Hydrogen gas on reaction.
Pb (s) + 2 H2SO4 → PbSO4 + SO2 + H2O
Lead Sulphuric acid lead Sulphate (II) Sulphur Dioxide Water
Note: Lead does not react with sulphuric acid, that’s why reaction takes place in the boiling solution. Lead on reacting with 2 moles of HSO4, forms lead sulphate (II), sulphur dioxide with the release of water.
Please send charlie’s monkeys and zebras in lead & hydrogen cages in mountains securely guarded by plato.
In the above given sentence, each bold alphabet denotes the elements of reactivity series in order of their reactivity from highest to lowest. You can understand this better by the table given below -
Question 1: Is Gold a Reactive Metal?
Answer: No, Gold is one of the least reactive elements among all the elements on the Periodic Table. Gold never reacts with oxygen present in the air, water, and also not with alkalis, that's why it never corrodes. However, it does react with halogens.
Aqua regia with a mixture of HCl and HNO3 in the ratio of 1: 3, is the only solution that can dissolve Gold.
Question 2: Why is Magnesium a Very Reactive Element?
Answer: Magnesium is at the fourth number in the reactivity series of elements and it reacts vigorously with oxygen, it gives white flames, thereby losing all its electrons.
Question 3: Write the Reactivity Order of Na, K, Li, and Ca with Cold Water in Tabular Form.
Reactivity with Cold Water
Very Quick / Violent reaction
Quick reaction with cold water
Question 4: Write the Reactivity Order of the Following Elements with Dilute Acids.
Reactivity with Dilute Acids
Very quick reaction
Comparatively slower than Ca and Mg
Slower than Zn
Hardly reacts with dilute acids