Reactivity Series - Definition, Uses, Characteristics, FAQs

What is reactivity series and which is the most reactive metal?

Reactivity series definition: The reactivity series is a collection of metals arranged in order of increasing reactivity. As a result, a reactivity series of metals can be defined as a group of metals arranged in decreasing order of reactivity. It's sometimes referred to as an activity series. Metals have reactivity due to their incomplete outer orbitals or their electrical structure. Because metals tend to lose electrons, they generate positively charged ions. Because their electrons are far from the positively charged nucleus, metals with high atomic numbers are more reactive. As a result, they can be simply removed. The table is the long tabular list of reactive metals:

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In a reactive series of metals, the most reactive element is placed at the top thus, the most reactive metal is Caesium and the least reactive metal is placed at the bottom of the reactive series of metals thus, the least reactive metal is platinum.

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The short trick to remembering reactivity series:

Potassium (Please) Sodium (Stop) Calcium (Calling) Magnesium (Me) Aluminum (A) Carbon (Careless) Zinc (Zebra) Iron (Instead) Tin (Try) Lead (Learning) Hydrogen (How) Copper (Copper) Silver (Saves) Gold (Gold)

Please stop calling me a careless zebra instead try learning how copper saves gold.

This statement helps to learn the reactive series of metals.

Important uses of Activity or reactive series:

We already know that a metal activity series is a list of metals arranged in declining order of their reactivities. The reactive series tells you whether or not a metal may displace another in a single displacement reaction. It also contains information on metal reactivity in the presence of water and acid.

1. Reaction of metals with water:

A metal hydroxide and hydrogen are generated when it reacts with water . Sodium, for example, reacts quickly with cold water:

2Na(s)+2H₂O(l)2NaOH(aq)+H₂(g)

The more reactive the metal, the faster the reaction. Aluminum is unique in that it is a reactive metal that does not corrode when exposed to water. The surface of the iot naturally generates a thin coating of aluminium oxide, which keeps water away from the metal beneath.

2. Reaction of metal with steam:

When magnesium is first added to water, it reacts slowly, but a coating of insoluble magnesium hydroxide forms. This shields the metal and prevents it from reacting. When steam is run over hot magnesium, however, a strong reaction occurs:

Mg(s)+H₂O(g)MgO(s)+H₂(g)

Magnesium is oxidised, gaining oxygen to form magnesium oxide, while water is reduced in this reaction. It loses oxygen in order to produce hydrogen. The relative resistance to oxidation of a metal is proportional to its position in the reactivity series; in general, the lower a metal's position in the reactivity series, the stronger its resistance to oxidation.

3. Reaction of metals with dilute acids:

A salt and hydrogen are generated when a metal combines with a dilute acid. Magnesium, for example, reacts quickly with dilute hydrochloric acids;

Mg(s)+2HCl(aq)MgCl₂(aq)+H₂(g)

The more reactive the metal, the quicker the reaction. A metal in the reactivity series below hydrogen will not react with dilute acids.

4. In Displacement reaction:

Only a metal that fits above it in the reactivity sequence can displace another metal from a complex. When a more reactive metal (one that forms positive ions more easily) displaces a less reactive reactive metal from a compound, a displacement reaction occurs.

Example- Magnesium is more reactive than copper, hence the reaction will be:

Mg(s)+CuSO₄(aq)MgSO₄(aq)+Cu(s)

platinum, however, is less reactive than copper and thus can't displace copper from the solution for copper sulphate. Silver is less reactive than copper and is therefore not removing the solution for copper sulphate.

5. In Extraction of metals:

Most metals are only present in compounds because they have already reacted with other elements. As a result, the metal must be removed from the ore containing the metal complex.

The below table shows the reactivity of common and most used metals which can react with water or acids:

Metals ranging from potassium to calcium are extremely reactive, reacting even with water. Acids can react with metals ranging from magnesium to lead. In normal settings, metals ranging from copper to platinum are highly unreactive and do not react with any other substance. This is why platinum and gold are resistant to corrosion and do not create oxides. Metals like zinc, aluminium, magnesium, and calcium, on the other hand, readily form oxide.

Non-metals in the reactivity series:

Although hydrogen is a nonmetal, it is included in the reactivity series because it aids in the comparison of metal reactivity and also used in extraction of metals. Carbon is also placed in the reactive series and metals like zinc and iron can be displaced by the oxides of carbon and metal like copper can be extracted using carbon and hydrogen.

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Reactivity series characteristics include:

• As we progress through the reactivity series, the electropositive character decreases. In the presence of oxygen, potassium and sodium make superoxide, but in the absence of oxygen, they produce their own oxides.

K+O₂→KO₂

• Because we progress down the reactivity series, metals' reducing power increases. As a result, potassium is the most powerful reducing agent.

• As we progress through the activity series, the tendency for metals to become oxidised is reduced.

• Also, as we progress down the reactivity scale, metals' capacity to convert water to hydrogen decreases. Because potassium and sodium are very reactive, they combine with cold water to produce hydrogen gas, which is ignited by the heat generated during the reaction.

2K+2H₂O→2KOH+H₂

• All metals in the activity series above hydrogen have the ability to liberate hydrogen gas by reducing hydrogen ions from dilute hydrochloric or sulphuric acid.

• A metal higher in the reactivity series can replace a metal lower in the series to form the latter metal's salt solutions. The faster the displacement reaction, the greater the gap between the locations of two metals.

• Common reducing agents are incapable of reducing metal oxides such as potassium, sodium, calcium, magnesium, and aluminum.

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