Properties of metals

No mattern how simillar the properties of metals appear to be, they also differ in other ways. E.g.

  • Sodium is soft and reacts violently with both air and water.
  • Iron also reacts with air and water but much more slowly, forming rust.
  • Gold remains totally unchanged after many hundreds of years.

Sodium is therefore said to be more reactive than iron and, in
turn, iron is said to be more reactive than gold.

Reactions of metals with air

Many metals such as sodium, potassium, calcium and magnesium react directly with oxygen to form oxides. For example, magnesium burns brightly in oxygen to form the white powder magnesium oxide.

Magnesium + oxygen → magnesium oxide
2Mg(s) + O2(g) → 2MgO(s)

MagnesiumMagnesium metal

Image Source

Magnesium oxideMagnesium oxide

Copper OxideUnoxidised copper wire (left), oxidised copper wire (right)

Reactions of metals with water

Reactive metals such as potassium, sodium and calcium react with cold water to produce the metal hydroxide and hydrogen gas. For example, the reaction of sodium with water produces sodium hydroxide and hydrogen.

Sodium + water → sodium hydroxide + hydrogen
2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)

The less reactive metals such as magnesium, zinc and iron react slowly with water at room temperature. They will, however, react more rapidly with steam. In their reaction with steam, the metal oxide and hydrogen are formed. For example, zinc produces zinc oxide and hydrogen gas.

Zinc + steam → zinc oxide + hydrogen
Zn(s) + H2O(g) → ZnO(s) + H2(g)

Zinc oxide is yellow when hot, white when cold.

Reactions of metals with dilute acids

Most metals react with dilute acids to produce a salt and hydrogen. For example magnesium reacts with dilute hydrochloric acid to produce magnesium chloride and hydrogen gas.

Magnesium + hydrochloric acid → magnesium chloride + hydrogen
Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)

Reactivity series of metals in order of decreasing reactivity
Reactivity seriesReaction with dilute acidReaction with air/oxygenReaction with water
Potassium (K)Reacts to produce salt and hydrogen gasBurn very brightly and vigorously to produce an oxideReacts with cold water to produce hydrogen
Sodium (Na)
Calcium (Ca)
Magnesium (Mg)Reacts with steam to produce hydrogen gas
Aluminium (Al)Burn to form an oxide with less vigour
Zinc (Zn)
Iron (Fe)
Lead (Pb)React slowly to form the oxideNo reaction with water or steam
Copper (Cu)No reaction with dilute acids
Silver (Ag)Does not react
Gold (Au)
Platinum (Pt)