Reactivity of metals

Metals react with oxygen to form metal oxides in oxidation reactions.

• •Metals react with oxygen to produce metal oxides.
• •The gain of oxygen by an element or compound is called oxidation.
• •The loss of oxygen from a compound is called reduction.
• •When magnesium reacts with oxygen, magnesium is oxidised to form magnesium oxide.

A metal's reactivity depends on its tendency to lose electrons and form positive ions.

• •Metals lose electrons to form positive ions when they react.
• •A more reactive metal will displace a less reactive metal from its compound in a solution.
• •Potassium, sodium, and lithium react violently with water, whereas metals like zinc and iron react with dilute acids.
• •Carbon and hydrogen are non-metals included in the reactivity series as reference points: carbon shows which metals can be extracted by reduction with carbon, and hydrogen shows which metals will react with dilute acids.

Unreactive metals are found in native form, while most metals must be extracted from their ores by reduction.

• •Unreactive metals such as gold are found as native metals directly in the Earth's crust.
• •Metals less reactive than carbon can be extracted from their oxides by reduction with carbon.
• •During reduction with carbon, carbon gains oxygen (is oxidised) and the metal oxide loses oxygen (is reduced).
• •Metals more reactive than carbon must be extracted using electrolysis.

Redox reactions involve the transfer of electrons between reacting species.

• •Oxidation occurs when an atom or ion loses electrons.
• •Reduction occurs when an atom or ion gains electrons.
• •Displacement reactions are redox reactions because one species is oxidised while another is reduced.
• •Ionic equations show electron transfer and omit spectator ions that do not change during the reaction.