The reactivity series of metals
The A list of elements in order of their reactivity, usually from most reactive to least reactive. of Shiny element that is a good conductor of electricity and heat, and which forms basic oxides. is a chart showing metals in order of decreasing A measure of how vigorously a substance will react. The more reactive it is, the greater its reactivity and the more vigorous its reactions will be.. In general, the more The tendency of a substance to undergo a chemical reaction. a metal is:
- the more vigorous its reactions are
- the more easily it loses Subatomic particle, with a negative charge and a negligible mass relative to protons and neutrons. in reactions to form positive Electrically charged particle, formed when an atom or molecule gains or loses electrons. (cations)
The table summarises some reactions of metals in the reactivity series. Hydrogen is shown for comparison.
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Reactions of metals with water
When a metal reacts with water, a metal hydroxide and hydrogen are formed.
For example, sodium reacts rapidly with cold water, melting into a ball, and 'fizzing' about the surface:
sodium + water → sodium hydroxide + hydrogen
2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
In general, the more reactive the metal, the more rapid the reaction is.
Reactions with steam
Metals that react slowly with cold water can react quickly with steam. In these reactions a metal oxide and hydrogen are produced.
Metal + steam → metal oxide + hydrogen
For example, magnesium reacts slowly with cold water. However, if steam is passed over hot magnesium, a vigorous reaction occurs:
Magnesium + steam → magnesium oxide + hydrogen
Mg(s) + H2O(g) → MgO(s) + H2(g)
Question
State the difference between the products formed when calcium reacts with cold water and when it reacts with steam.
Calcium hydroxide forms when it reacts with water, but calcium oxide forms when it reacts with steam.
Reactions of metals with dilute acids
When a metal reacts with a dilute Substance producing more hydrogen ions than hydroxide ions when dissolved in water. , a The substance formed when the hydrogen ion in an acid is replaced by a metal ion. and hydrogen are formed.
Metal + acid → salt + hydrogen
For example, magnesium reacts rapidly with dilute hydrochloric acid:
Magnesium + hydrochloric acid → magnesium chloride + hydrogen
Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
The more reactive the metal, the more rapid the reaction is. A metal below hydrogen in the reactivity series will not react with dilute acids.
Question
Platinum is placed below gold in the reactivity series. Predict its reaction with dilute acids and explain your answer.
Platinum will not react with dilute acids. Metals below hydrogen in the reactivity series do not react with dilute acids, and both gold and platinum are placed below hydrogen.
In the reactions of metals with water, steam and acids, the metals lose electrons and form cations. The metal is The gain of oxygen, or loss of electrons, by a substance during a chemical reaction. and the water is The loss of oxygen, gain of electrons, or gain of hydrogen by a substance during a chemical reaction..
A metal's relative tendency to form cations and its resistance to oxidation are both related to its position in the reactivity series. In general:
- the higher up a metal, the greater the tendency to form cations
- the lower down a metal, the greater its resistance to oxidation
