Reactivity Series

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What is the Reactivity Series?

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. 


Long Tabular Form of the Reactivity Series 

Symbol of Element 

Name of Element 


Potassium 



Most Reactive 

Na 

Sodium 

↑ Reactivity Increases

↓Reactivity Decreases

Ca

Calcium 

Mg 

Magnesium 

Al 

Aluminium 

Zn 

Zinc 

Fe 

Iron 

Pb 

Lead 

Hydrogen 

Cu

Copper 

Hg

Mercury 

Ag 

Silver 

Au 

Gold 

Pt 

Platinum 

Least reactive 


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. 


Salient Features 

  • 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. 


Important Uses of Reactivity Series – 

  • 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:

Reaction 1:   

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.


Reaction 2:

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: 

Reaction 1:   

 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.


Reaction 2:   

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.


Short Trick to Remember Reactivity Series – 

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 - 


Elements of Reactivity Series 

Sentence to Remember the Series 

K (Potassium)

Please 

Na (Sodium)

Send 

Ca (Calcium)

Charlie’s 

Mg (Magnesium)

Monkey 

Al (Aluminum)

And 

Zn (Zinc)

Zebra 

Fe (Iron)

In 

Pb (Lead)

Lead &

H (Hydrogen)

Hydrogen 

Cu (Copper)

Cages 

Hg (Mercury)

in Mountains 

Ag (Silver)

Securely 

Au (Gold)

Guarded by

Pt (Platinum)

Plato 

FAQ (Frequently Asked Questions)

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.

Answer: 


Metal

Reactivity with Cold Water

Potassium

Very Quick / Violent reaction

Sodium

Very Quick

Lithium

Quick reaction with cold water

Calcium

Very Slow

Question 4: Write the Reactivity Order of the Following Elements with Dilute Acids.

  1. Ca

  2. Mg

  3. Zn

  4. Fe

  5. Cu

  6. Ag

  7. Au

Answer: 


Metal

Reactivity with Dilute Acids

Ca

Very quick reaction

Mg

Quick reaction

Zn

Comparatively slower than Ca and Mg

Fe

Slower than Zn

Cu

Very slow

Ag

Hardly reacts with dilute acids

Au

Unreactive