- Recall the bonding arrangement in metals and how this links to their properties.
Diagram showing bonding and structure in metals
- Based on how they react with other substances, a reactivity series can be produced in which the metals are placed in order of their 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.
- Note that although carbon and hydrogen are nonmetals, they are included in the series as they are useful in extracting metals from their oxides by reduction processes.
Diagram of the reactivity series of metals
- There are several reactivity series mnemonics to help you remember the order of the metals.
- One that we like goes as follows: “Please send lions, cats, monkeys and cute zebras into hot countries signed Gordon”.
Mnemonic of the reactivity series of metals
Chemical properties of metals
- The chemistry of metals is studied by analysing their reactions with water, dilute acid and oxygen.
Reactivity with water
- Some metals react with water, either warm or cold, or with steam.
- Metals that react with cold water form a metal hydroxide and hydrogen gas, for example calcium:
Ca + 2H2O → Ca(OH)2 + H2
- Metals that react with steam form metal oxide and hydrogen gas, for example zinc:
Zn + H2O → ZnO + H2
Reactivity with acids
- Most metals react with dilute acids such as HCl.
- When acids and metals react, the hydrogen atom in the acid is replaced by the metal atom to produce a salt and hydrogen gas, for example iron:
Fe + 2HCI → FeCl2 + H2
Reactivity with oxygen
- Unreactive metals such as gold and copper do not react with acids.
- Some reactive metals such as the alkali metals react with oxygen.
- Copper and iron can also react with oxygen although much more slowly.
- When metals react with oxygen a metal oxide is formed, for example copper:
2Cu + O2→ 2CuO
The nature of the reactions of metals with water, dilute acid and oxygen
Displacement reactions between metals & metal oxides
- The reactivity of metals increases going up the reactivity series.
- This means that a more reactive metal will displace a less reactive metal from its oxide by heating in a displacement reaction .
- For example it is possible to reduce copper(II) oxide by heating it with zinc.
- The reducing agent in the reaction is magnesium:
CuO + Zn ⟶ Cu + ZnO
Other displacement reactions
Displacement reactions between metals & aqueous solutions of metal salts
- The reactivity between two metals can be compared using displacement reactions in salt solutions of one of the metals.
- This is easily seen as the more reactive metal slowly disappears from the solution, displacing the less reactive metal.
- For example, magnesium is a reactive metal and can displace copper from a copper sulfate solution:
Mg + CuSO4→ MgSO4 + Cu
- The blue color of the CuSO4solution fades as colorless magnesium sulfate solution is formed.
- Copper coats the surface of the magnesium and also forms solid metal which falls to the bottom of the beaker.
Diagram showing the colour change when magnesium displaces copper from copper sulfate
Other displacement reactions