Summary Group 2 Notes - AQA Chemistry A Level

Group 2
Solubility
 To test solubility of hydroxides, add solutions containing each Group 2 ion to a solution
containing hydroxide ions
 To test solubility of sulfates, add solutions containing each Group 2 ion to a solution containing
sulfate ions
 Solubility of hydroxides increases DOWN the group
o Mg2+(aq) + 2OH-(aq) -> Mg(OH)2(s) – insoluble
o Ca2+(aq) + 2OH-(aq) -> Ca(OH)2(aq) – slightly soluble
o Sr2+(aq) + 2OH-(aq) -> Sr(OH)2(aq) – soluble
o Ba2+(aq) + 2OH-(aq) -> Ba(OH)2(aq) – soluble
 Solubility of sulfates increases UP the group
o Mg2+(aq) + SO42-(aq) -> Mg(OH)2(aq) – soluble
o Ca2+(aq) + SO42-(aq) -> Ca(OH)2(aq) – slightly soluble
o Sr2+(aq) + SO42-(aq) -> Sr(OH)2(s) – insoluble
o Ba2+(aq) + SO42-(aq) -> Ba(OH)2(s) – insoluble

Sulfate Ions
 Add hydrochloric acid to the solution being tested
o Removes other ions which could form precipitates and interfere with the test
 Add barium chloride to the solution being tested
o Produces a white precipitate with sulfate ions

Physical Properties
Atomic Radius
 Increases
o More electron shells

First Ionisation Energy
 Decreases
o Increasing atomic radius
o More shielding
 Less attraction between nucleus and electron – easier to remove

Melting Points
 Decreases
o Ions get larger
o Weaker electrostatic attraction between positive metal ions and sea of delocalised
electrons

Reactions with Water
 Mg