Chapter 8 Reactivity Trends Flashcards
What are Group 2 elements?
Alkaline metals, comes from alkaline properties of metal hydroxides
Reactive, do not occur in elemental form naturally, found in stable compounds
What is the reactivity trend of Group 2 elements?
Act as reducing agents
Reactivity increases down the group
What are the reactions of Group 2 elements?
With oxygen to form metal oxide
With water to form alkaline hydroxide and hydrogen gas
With dilute acids to form salt and hydrogen gas
What is the ionisation energy trend?
Ionisation energy decreases as the attraction between the nucleus and outer electrons decrease as a result of increasing atomic radius and increasing shielding
What are the properties of Group 2 elements?
Group 2 hydroxides are slightly soluble in water, solubility of metal hydroxides in water increases down the group, so the resulting solution contain more OH- and more alkaline
When solution becomes saturated, further metal and hydroxide ions form a solid precipitate
pH and alkalinity increases down the group
What are halogens?
Halogens are the most reactive non-metallic group
Elements don’t occur in elemental form in nature
Occur in stable halide ions dissolved in sea water or combined with Na or K as solid deposits
What are the properties of halogens at room temperature?
Chlorine- pale green
Bromine- toxic and vaporises readily
Iodine- solid with grey-black crystals
What are the properties of halogen gases?
Boiling point increases down the group as there is more electrons, stronger London forces which more energy is required to break intermolecular force
What is displacement reactions?
When the more reactive halides displace halogens in the solution.
The solution changes colour which indicates the halogen displacing the halide from the solution
What is the reactivity trend of halogens?
Reactivity decreases as atomic radius increases, shielding increases, nuclear attraction decreases
What is disproportionation?
Redox reaction which the same element is oxidised and reduced
What is the reaction of halide ions with aqueous silver ions?
Form precipitates of silver halides
Silver chloride- white
Silver bromide- cream coloured
Silver iodide- yellow
Aqueous ammonia tests the solubility, iodide is insoluble in aqueous ammonia
What is the carbonate reaction?
Carbonates react with acid to form carbon dioxide .
Add dilute nitric acid to the solid or solution to be tested. If there are bubbles, unknown could be a carbonate. Bubble the gas through lime water, if a white precipitate calcium carbonate is formed, the gas is carbon dioxide
What is the sulfate test?
Barium nitrate is used to test sulfate to form insoluble barium sulfate
How do we test for ammonium?
Aqueous ammonium ions and aqueous hydroxide ions react to form NH3, which ammonia could be smelled and turns blue on pH indicator paper
What is the reaction sequence of testing?
Carbonate reaction- sulfate test- halide test
