Group 7 Halogens Flashcards
Give some properties of the halogens
Have 7 electrons in their outer shell and are in the P block.
Generally diatomic
Have different appearances at room temperature
Have low melting and boiling point as only weak intermolecular forces exist (van der waals)
What is the changes of state that occur down the group and what are their appearances (colour) for each element?
F2 - gas (yellow)
Cl2 - gas (green)
Br2 - liquid ( orangey browny red)
I2 - solid (black)
At2 - solid
What happens to the atomic size of the halogens down the group?
Increases down the group
Due to more electrons in the shells and therefore there are more shells so the atomic radius increase
What is the trend in electronegativity down the group?
Decreases down the group
More electron shells and therefor increased shielding between the outer electrons and the central nucleus by the inner electron shells
This means the outer electrons have less attractive forces acting upon them and are therefore more easily lost
What is the trend in boiling point down the group?
Increases down the group
Each element has an extra shell of electrons and therefore a larger atomic radius
His means there is a greater surface area for a greater abundance of van der waals forces of attraction to act between so the boiling point increases as more energy is required to break the abundance of van der waals
What is the trend in reactivity of the halogens down the group?
Halogens are very reactive
Highly electronegative elements which only require 1 extra electron to obtain a full outer shell.
Down the group reactivity decreases as there are more shells and therefore increased shielding. This means there is less attraction between the positive nucleus and the negative surrounding electrons so fewer electrons are gained producing the full octect outer shell.
Why are halogens strong oxidising agents?
They themselves can easily be reduced by accepting an electron and hence will oxidise another species
What type of ions do the halogens produce?
Halide ions
Cl-
Br-
What is a displacement reaction?
Where a more reactive species will displace a less reactive species from a solution
What is disproportionation?
A disproportionation reaction is one where the same species is both oxidised and reduced in the same reaction
What happens when chlorine is added to water?
Chlorine can dissolve in water to produce HCL or HClO ( products of this reaction can be used to kill bacteria and is used to sanitise water)
What happens when chlorine is added to an alkali?
With cold alkali ( eg NaOH) chlorine will react producing NaCl or NaClO
These can be used as disinfectant or bleaching agents and weed killers
What are the advantages and disadvantages of using chlorine disproportionation properties?
Advantages:
Can be used to sanities water
Prevents the spread of infections (especially water born diseases)
Disadvantages:
Water is chlorinated without direct consent
Chlorine could react with organic matter forming chlorinated hydrocarbons
( could cause cancer)
What happens in the trends of oxidation and reduction for halogens and Halide ions down the group?
Halogens are oxidising agents
Halide ions are reducing agents
Down the group
Oxidising power of halogens decreases
Reducing power of halide ions increases
What happens when halide ions react with conc sulphuric acid?
Halide ions are reducing agents
Sulphuric acid is an oxidising agent
Three possible reactions:
Produce sulphuric dioxide
Produce sulphur
Produce hydrogen sulphide
