Reactivity Trends

Group 2 elements are reducing agents. They become stronger reducing agents down a group.

Reactivity increases down the group because the ionisation energies decrease.

Group 2 oxides are only slightly soluble, forming a precipitate when the solution is saturated. 

The solubility of hydroxides increases down the group along with pH and alkalinity.

Boiling point increases down the group.

Halogens form lattices with simple molecular structures when solid.

Halogens are oxidising agents. They become weaker down the group.

Halide ions are reducing agents. They get more powerful down the group.

If the halogen added is more reactive than the halide present a reaction takes place and the solution changes colour.

Cyclohexane can be used to distinguish between aqueous bromine and iodine as they dissolve in it more readily than in water.

Reactivity decreases down the group because atomic radius and sheilding increases resulting in less nuclear attraction.

Disproportionation is where the same element is oxidised and reduced.

The carbonate test: dilute nitric acid is added to an unknown solution. If gas is produced, bubble it trough lime water, if the lime water turns cloudy then carbonate ions are present.

The sulfate test: barium nitrate is added to a solution. If a white precipiate forms sulfate ions are present.

The hailde test: silver nitrate is added to a solution. If a white precipitate forms, chloride ions are present. If a cream precipitate forms, bromide ions are present. If a yellow precipitate forms, iodide ions are present.

Silver chloride is soluble in dilute ammonia. Sliver bromide is soluble in concentrated ammonia. Silver iodide is insoluble in concentrated ammonia.

The ammonium test: ammonium ions and sodium hydroxide are heated, producing ammonia gas. If moist pH indicator paper turns blue, ammonia gas is present.