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
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
