2.3 Group 7 Flashcards
What does halogen mean?
Halo = salt Gen = maker/producer
What are the physical appearances of the halogens at room temperature?
Fluorine - yellow gas
Chlorine - green gas
Bromine - orange liquid
Iodine - grey/black solid
What is the trend for atomic radius of the halogens?
Atomic radius increases down the group
Why does the atomic radius increase down the group?
There are more principal energy levels = larger atomic radius
Because of more electrons
What is the trend for boiling points of the halogens?
Boiling point increase going down the group
Why does the boiling point increase down the group?
Atomic radius increases due to increased number of electrons therefore greater van der Waals forces which require more energy to overcome
What are some physical properties of halogens?
Similar electronic structure
Non-metals
Diatomic molecules
Toxic coloured vapours
What is the trend of electronegativity in the halogens?
Electronegativity decreases down group 7
Why does electronegativity decrease down the group?
Because…
Nuclear charge increases
Atomic radius increases
Electron shielding increases
What is the trend in the halogens oxidising ability?
As you go down group 7 oxidising ability decreases
Which halogen is the most powerful oxidising agent? Why don’t we look at it?
Fluorine
It reacts with water therefore the reactions in solutions can’t be easily investigated
What does displacement reactions of halogens include?
Salt solution: Potassium chloride, bromide, iodide (doesn’t have to be potassium- any spectator ion)
Halogen solution: Cl2, Br2, I2 (aq)
What are the colours of the halogen solutions used in displacement reactions?
Chlorine - colourless
Bromine - yellow
Iodine - brown
What can’t happen in a displacement reaction?
Chlorine can’t oxidise itself
Bromine can’t oxidise itself
Iodine can’t oxidise itself
What are the only displacement reactions that can happen?
Chlorine oxidises bromide
Chlorine oxidises iodide
Bromine oxidises iodide
Which halogen seems to work best in the displacement reactions? Why?
Chlorine
It has the smallest atomic radius
Therefore the electron being accepted is closer to the nucleus - and more strongly attracted
What are the colour changes in the displacement reactions?
Chlorine oxidises Bromide
Colourless to yellow
Chlorine oxidises Iodide
Colourless to brown
Bromine oxidises Iodine
Yellow to brown
What is the trend in halogens for reducing ability? Why?
Reducing power increases down the group
Ionic radius increases therefore electrons are lost more easily
What halides are used in the reactions with concentrated sulphuric acid?
(Sodium)
Fluoride, chloride, bromide, iodide
(Sodium doesn’t matter as only a spectator ion is required)
What are the reaction products produced when reacting concentrated sulphuric acid with Sodium Chloride/Fluoride? Observations?
HCl/HF - Misty fumes
What are the reaction products produced when reacting concentrated sulphuric acid with sodium bromide? Observations?
HBr - Misty fumes
Br2 - Brown fumes (temperature dependent)
SO2 - colourless, choking gas
What are the reaction products produced when reacting concentrated sulphuric acid with sodium iodide? Observations?
HI - Misty fumes I2 - Purple fumes + black solid SO2 - colourless, choking gas S - yellow solid H2S - colourless gas, bad egg smell
What test can you tell HF/HCl/HBr/HI is produced?
Turns Universal indicator paper red
What test can you tell SO2 is produced?
Turns acidified Potassium dichromate (VI) from orange to green
