ES - Group 7 The halogens Flashcards
What are halogens?
The highly reactive non-metals of group 7.
What happens to the volatility of the elements as you go down group 7?
Become less volatile.
What is volatility?
A measure of how easy it is to vaporise something (turn it into a gas).
Why does the volatility of the group 7 elements decrease as you go down the group?
Because of the increasing strength of the instantaneous dipole-induced dipole bonds - these increase as the size and relative mass of the atoms increase.
What can you use to see the trend in volatility of the group 7 elements?
Their appearance at RTP.
What is the appearance of fluorine at RTP?
Pale yellow gas.
What is the appearance of chlorine at RTP?
Yellow-green gas.
What is the appearance of bromine at RTP?
Red-brown liquid.
What is the appearance of iodine at RTP?
Shiny grey solid.
Compare the solubility of the halogens in organic solvents and in water:
More soluble in organic solvents than in water.
What do halogens exist as in their natural state?
Covalent diatomic molecules.
Why do the halogens have a low solubility in water?
Because they’re covalent and non-polar.
What is the solubility of halogens like in water?
Low.
What is the solubility of halogens like in organic solvents?
High - dissolve easily.
What is the colour of chlorine in water?
Virtually colourless.
What is the colour of bromine in water?
Yellow/orange.
What is the colour of iodine in water?
Brown.
What is the colour of chlorine in hexane?
Virtually colourless.
What is the colour of bromine in hexane?
Orange/red.
What is the colour of iodine in hexane?
Pink/violet.
How does the reactivity of the halogens change down the group?
They get less reactive as you go down the group.
How do halogen atoms react?
By gaining an electron in their outer p sub-shell.
In reaction, are halogens oxidised or reduced?
Reduced - they gain electrons.
Are halogens oxidising or reducing agents?
Oxidising - as they are reduced, they oxidise another substance (it’s a redox reaction).
Why do the halogens get less reactive down the group?
The atoms become larger, so their outer electrons are further from the nucleus.
The outer electrons are also shielded more from the attraction of the positive nucleus, because there are more inner electrons.
This makes it harder for larger atoms to attract the electron needed to form an ion - so larger atoms are less reactive.
What can halogens do to halide ions from solution?
Displace them.
What is a displacement reaction?
A type of reaction where one reactant replaces another reactant in a compound.
What will displace what in a displacement reaction?
A more reactive halogen will displace a less reactive halide in a solution.
What will chlorine displace?
Bromide and iodide ions.
What will bromine displace?
Iodide but not chloride ions.
What will iodine displace?
Not chloride or bromide ions.
What type of reaction is a displacement reaction between halogens and halides?
A redox reaction.
The thing that is displaced is…
…oxidised.
The thing that does the displacing is…
…reduced.
What change in appearance would there be if a reaction takes place between a halogen and halide?
A colour change.
If bromide is displaced and bromine is formed, what colour would the reaction mixture turn?
Orange.
If iodide is displaced and iodine is formed, what colour would the reaction mixture turn?
Brown.
How can you make the colour change due to a displacement reaction easier to see?
Shake the reaction mixture with an organic solvent like hexane as the halogen that is present will dissolve in the organic solvent which settles out as a distinct layer above the aqueous solution.
