Group 2

group 2 1

General Properties

  • Form ionic compounds in they have an oxidation state of 2
  • Form ionic compounds with a higher Lattice energy when compared to the alkali metal compounds.
  • Less thermally stable then group 1
  • Ionisation energy decreases down the group

Physical Properties

  • Higher densities then group 1
  • Grey in colour

Chemical Properties

With O2

Group 2 metals react in air to form the simple oxide, except for barium, which produces the superoxide.

2Be (s) + O2(g) à 2BeO(s)

2Mg (s) + O2(g) à 2MgO(s)

2Ca (s) + O2(g) à 2CaO(s)

Ba (s) + O2(g) à BeO2(s)

With H2O

The reactivity of group 2 compounds with water increases down the group.

Beryllium does not react with water.

 

Magnesium reacts with steam to produce the oxide and Hydrogen

Mg + H2O(g) à MgO + H2

Calcium and Barium react with water to produce the hydroxide and Hydrogen.

Ca + 2H2O(l) à Ca(OH)2 + 2H2

Hydroxides

Solubility of hydroxides increase down the group. Magnesium hydroxide is insoluble while barium hydroxide is completely soluble.

Preparation of Magnesium hydroxide is obtained by a precipitation reaction.

All group 2 hydroxides break down when heated to give the oxide and water.

Mg(OH)2 à MgO + H2O

Carbonates

These are prepared by precipitation reactions with the solubility decreasing down the group.

All carbonates are thermally unstable to give CO2 and the oxide.

CaCO3 à CaO + CO2

Nitrates

All nitrates break down to produce the oxide, nitrogen dioxide and oxygen.

2Mg(NO3)2 à 2MgO + 4NO2 + O2

 

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