Reactivity Series of Metals

Reactivity Series of Metals

• The reactivity series of metals is a list of metals in order of reactivity based on their reactions with water and acids.
• The series includes metals and non-metals (hydrogen and carbon) and is used to compare the reactivity of different metals.

Reactivity with Cold Water

• The more reactive metals (potassium, sodium, and calcium) react with cold water to form a metal hydroxide and hydrogen gas.
• The reaction is: metal + water → metal hydroxide + hydrogen
• Examples: calcium (Ca + 2H2O → Ca(OH)2 + H2) and potassium (2K + 2H2O → 2KOH + H2)

Reactivity with Steam

• Metals below calcium in the reactivity series react with steam to form a metal oxide and hydrogen gas.
• The reaction is: metal + steam → metal oxide + hydrogen
• Example: magnesium (Mg + H2O → MgO + H2)

Reactivity with Dilute Acids

• Only metals above hydrogen in the reactivity series react with dilute acids.
• The more reactive the metal, the more vigorous the reaction will be.
• Metals that are placed high on the reactivity series (such as potassium and sodium) react explosively with acids.
• The reaction is: metal + acid → salt + hydrogen
• Examples: magnesium (Mg + H2SO4 → MgSO4 + H2) and zinc (Zn + H2SO4 → ZnSO4 + H2)

Reactivity with Oxygen

• Some reactive metals (such as alkali metals) react easily with oxygen.
• The reaction is: metal + oxygen → metal oxide
• Example: copper (2Cu + O2 → 2CuO)

Deducing the Order of Reactivity

• The order of reactivity of metals can be deduced by making experimental observations of reactions between metals and water, acids, and oxygen.
• The more vigorous the reaction of the metal, the higher up the reactivity series the metal is.
• A combination of reactions may be needed to determine the order of reactivity.

Explaining Reactivity

• Metal atoms form positive ions by loss of electrons when they react with other substances.
• The tendency of a metal to lose electrons is a measure of how reactive the metal is.
• A metal that is high up on the series loses electrons easily and is thus more reactive than one which is lower down on the series.

Displacement Reactions

• Any metal will displace another metal that is below it in the reactivity series from a solution of one of its salts.
• This is because more reactive metals lose electrons and form ions more readily than less reactive metals, making them better reducing agents.
• The less reactive metal is a better electron acceptor than the more reactive metal, thus the less reactive metal is reduced.

Example of Displacement Reaction

• Magnesium + copper sulfate → magnesium sulfate + copper
• Magnesium loses its electrons more easily and the ion of the less reactive metal, copper, will gain these electrons to form elemental copper.

Relative Reactivity Order

• By combining different metals and metal salts solutions, it is possible to come up with a relative reactivity order.
• The order of reactivity of the metals tested can be deduced as: Mg > Zn > Fe > Cu > Ag.

Reactivity of Aluminium

• Aluminium is high in the reactivity series, but in reality, it does not react with water and the reaction with dilute acids can be quite slow.
• This is because it reacts readily with oxygen, forming a protective layer of aluminium oxide which is very thin.
• This layer prevents reaction with water and dilute acids, so aluminium can behave as if it is unreactive.

Learn about the reactivity series of metals, how it's produced, and its applications in understanding metal reactions with water and acids.