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The Reactivity Series of Metals

Although most metals are usually electropositive in nature and lose electrons in a chemical reaction they do not react with the same vigour or speed. Metals display different reactions towards different substances. The greater the ease with which an element loses its electrons and acquires a positive charge, the greater is its reactivity. Further, the greater the number of shells and lesser the number of valence electrons, the greater is the reactivity of the metal. The activity series of metals, arranges all metals in order of their decreasing chemical activity. As we go down the activity series from potassium to gold the ease with which a metal loses electrons, and forms positive ions in solutions, decreases.

 

The Most Reactive and Least Reactive Metals

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The most active metal, potassium, is at the top of the list and the least reactive metal, gold, is at the bottom of the list. Although hydrogen is a non-metal it is included in the activity series due to the fact that it behaves like a metal in most chemical reactions i.e., the hydrogen ion has a positive charge [H+] like other metals.

reactivity series of metals
Element Symbol Group Number
Potassium K 1
Sodium Na 1
Lithium Li 1
Calcium Ca 2
Magnesium Mg 2
aluminium Al 3
Carbon C 4 (non-metal)
Zinc Zn Transition metal
Iron Fe Transition metal
Tin Sn 4
Lead Pb 4
Hydrogen H Non-metal
Copper Cu Transition metal
Silver Ag Transition metal
Gold Au Transition metal
Platinum Pt Transition metal


  • The higher the metal in the series, the more reactive it is i.e., its reaction is fast and more exothermic.
  • This also implies that the reverse reaction becomes more difficult i.e., the more reactive a metal, the more difficult it is to extract from its ore. The metal is also more susceptible to corrosion with oxygen and water.
  • The reactivity series can be established by observation of the reaction of metals with water, oxygen or acids.
  • Within the general reactivity or activity series there are some periodic table trends:
  • Down Group 1 (I) the "Alkali Metals" the activity increases Cs > Rb > K > Na > Li. Down Group 2 (II) the activity increases e.g., Ca > Mg. On the same period, the Group 1 metal is more reactive than the group II metal, and the group II metal is more reactive than the Group III metal, and all three are more reactive than the "Transition Metals". e.g., Na > Mg > Al (on Period 3) and K > Ca > Ga > Fe/Cu/Zn etc. (on Period 4)

Two non-metals, carbon and hydrogen are important chemical reference points with regard to the method of metal extraction and reactivity towards acids. Metals above carbon cannot be extracted by carbon reduction and are usually extracted by electrolysis. Metals below hydrogen will not displace hydrogen from acids:

Activity Series of Various Metals

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Below are the list of various metals and the reactivity and reactions of these metals:

Metals Reactivity and reactions
Potassium K Very reactive, very rapid with cold water forming the alkali potassium hydroxide and hydrogen gas(which is ignited).
2K+2H2O(l) image2KOH(aq) +H2(g)
Sodium Na Fast reaction with cold water forming the alkali sodium hydroxide and hydrogen gas.
2Na(s) + 2H2O(l) image 2NaOH(aq) + H2(g)

The reaction of sodium with water-the sodium melts to a silvery ball and fizzes as it spins over the water. The rapid exothermic reaction produces a colourless gas that gives a squeaky pop! with a lit splint-hydrogen. Universal indicator will turn from green to purple/violet-the strong alkali sodium hydroxide is formed. The sodium floats because it is less dense than water.
Calcium Ca Quite reactive with cold water forming the moderately soluble alkali calcium hydroxide and hydrogen gas.
Ca(s) +2H2O(l) image Ca(OH)2(aq/s) + H2(g)

Very reactive with dilute hydrochloric acid forming the colourless soluble salt calcium chloride and hydrogen gas.

Ca(s) +2HCl(g) image CaCl2(aq) +H2(g)

Not very reactive with dilute sulphuric acid because the colourless calcium sulphate formed is not very soluble and coats the metal inhibiting the reaction.

Ca(s) + H2SO4(aq) imageCaSO4(s) + H2(g)
Magnesium Mg Slow reaction with water forming the slightly soluble alkali magnesium hydroxide and hydrogen gas.
Mg(s) +2H2O(l) imageMg(OH)2(aq/s) +H2(g)  

With steam, the reaction is faster with heated magnesium and a white powder magnesium oxide is formed along with hydrogen.

Magnesium will burn with a bright white flame in steam, if previously ignited in air.

Mg(s) + H2O(g) image MgO(s) + H2(g)

In fact it will even burn in carbon dioxide forming black specks of carbon!

2Mg(s) +CO2(g) image 2MgO(s) + C(s)

Very reactive with dilute hydrochloric acid forming the colourless soluble salt, magnesium chloride and hydrogen gas.

Mg(s) +2HCl(aq) image MgCl2(aq) +H2(g)

Very reactive with dilute sulphuric acid forming colourless soluble magnesium sulphate and hydrogen.

Mg(s) +H2SO4(aq) image MgSO4(aq) + H2(g)

Aluminium Al Aluminium has no reaction with water or steam due to a protective aluminium oxide layer of Al2O3. Slow reaction with dilute hydrochloric acid to form a colourless soluble salt aluminium chloride and hydrogen gas.
2Al(s) +6HCl(aq) image 2AlCl3(aq) + 3H2(g)

The reaction with dilute sulphuric acid is extremely slow to form colourless aluminium sulphate and hydrogen.

2Al(s +3H2SO4(aq)imageAl2(SO4)3(aq) + 3H2(g)
(Carbon C,a non-metal) Elements higher than carbon i.e aluminium and the more reactive metals must be extracted by electrolysis (or displacing it with an even more reactive metal). Metals below it, i.e., zinc or a less reactive can be extracted by reducing the hot metal oxide with carbon.
Zinc Zn No reaction with cold water. When the metal is heated in steam zinc, oxide and hydrogen are formed.
Zn(s) + H2O(g) image ZnO(s) + H2(g)

Quite reactive with dilute hydrochloric acid forming the colourless soluble salt zinc chloride and hydrogen gas.

Zn(s) +2HCl(aq) image ZnCl2(aq) + H2(g)

Quite reactive with dilute sulphuric acid forming the colourless soluble salt zinc sulphate and hydrogen gas.

Zn(s) + H2SO4(g) image ZnSO4(s) + H2(g)  

(this reaction is catalysed by adding a trace of copper sulphate solution)

Zinc can be extracted by reducing the hot metal oxide on heating with carbon

2ZnO(s) + C(s) image 2Zn(s) + CO2(g)

A zinc coating (galvanizing) is used to protect iron from rusting.

Iron Fe No reaction with cold water (rusting is a joint reaction with oxygen). When the metal is heated in steam an iron oxide (unusual formula) and hydrogen are formed. This oxide is 'technically' Iron (III, II) oxide!
3Fe(s) + 4H2O(g) image Fe3O4(s) +4H2(g)

Slow reaction with dilute hydrochloric acid forming the soluble pale green salt Iron (II) chloride and hydrogen gas.

Fe(s) + 2HCl(aq) imageFeCl2(aq) + H2(g)

Slow reaction with dilute sulphuric acid forming the soluble pale green salt Iron (II) sulphate and hydrogen gas.

Fe(s) + 2H2SO4(g) image FeSO4(s) + H2(g)

Iron can be extracted by reducing the hot metal oxide on heating with carbon monoxide formed from carbon in the blast furnace e.g.,

Fe2O3(s) +3CO(g) image 2Fe(s) +3CO2(g)  

Fe3O4(s) +4CO(g) image 3Fe(s) +4CO2(g)

(Hydrogen H non-metal) None of the metals below hydrogen can react with acids to form hydrogen gas. They are least easily corroded metals and partly accounts for their value and uses in jewellery, electrical contacts etc.
Copper Cu No reaction with cold water or when heated in steam. No reaction with dilute hydrochloric acid or dilute sulphuric acid. Copper can be extracted by reducing the hot black metal oxide on heating with carbon.
2CuO(s) + C(s) image2Cu(s) +CO2(g)
Silver Ag No reaction with cold water or when heated in steam. No reaction with dilute hydrochloric acid or dilute sulphuric acid. Silver can be extracted by reduction but can be found 'native' as the element.
Gold Au No reaction with cold water or when heated in steam. No reaction with dilute hydrochloric acid or dilute sulphuric acid. Gold can be readily extracted from its ores easily by reduction but it is usually found 'native'. Pure gold is 24 carat.
Platinum Pt No reaction with cold water or when heated in steam. No reaction with dilute hydrochloric acid or dilute sulphuric acid. Like gold, it is a very rare metal. It is used in expensive jewellery, laboratory ware (inert crucible container) as a industrial catalyst, and catalytic converters in car exhausts.

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