Group 17 Flashcards
What are group 17 elements known as ?
halogens
What is the bonding and structure in Group 17 elements ?
- simple covalent molecules
- London forces between molecules
State and explain the trend in boiling points down group 17.
- number of electrons increases, so there are more London forces
- more energy is required to overcome the,
- so boiling point decreases down the group
Do Group 17 elements have a high or low boiling point and why ?
low, as they are simple diatomic molecules with London forces between molecules
Why are halogens oxidising agents ?
they oxidise other species while getting reduced themselves
State and explain the trend in reactivity down Group 17.
- shielding increases
- so atomic radius increases and nuclear attraction decreases
- so less energy is released when an electron is gained
- so reactivity decreases going down the group
What colour is Cl2 in water and in cyclohexane ?
water : pale green
cyclohexane : pale green
What colour is Br2 in water and in cyclohexane ?
water : orange
cyclohexane : orange
What colour is I2 in water and in cyclohexane ?
water : brown
cyclohexane : violet
What happens when Cl2 is added to Cl- in water and in cyclohexane ?
water : pale green
cyclohexane : pale green
- no reaction
What happens when Br2 is added to Cl- in water and cyclohexane ?
water : orange
cyclohexane : orange
- no reaction
What happens when I2 is added to Cl- in water and cyclohexane ?
water : brown
cyclohexane : violet
- no reaction
What happens when Cl2 is added to Br- in water and in cyclohexane ?
water : orange
cyclohexane : orange
- chlorine displaces bromide ions
What happens when Br2 is added to Br- in water and in cyclohexane ?
water : orange
cyclohexane : orange
- no reaction
What happens when I2 is added to Br- in water and in cyclohexane ?
water : brown
cyclohexane : violet
- no reaction
What happens when Cl2 is added to I- in water and in cyclohexane ?
water : brown
cyclohexane : violet
- chlorine displaces iodide ions
What happens when Br2 is added to I- in water and in cyclohexane ?
water : brown
cyclohexane : violet
- bromine displaces iodide ions
What happens when I2 is added to I- in water and in cyclohexane ?
water : brown
cyclohexane : violet
- no reaction
What are the properties of Group 17 elements and compounds ?
- become less reactive going down the group
- form diatomic molecules with strong covalent bonds
- have weak London forces between molecules
- good oxidising agents
What is the test and result of halide ions ?
test : add aqueous silver nitrate
result : chloride ions = white precipitate ; bromide ions = cream precipitate ; iodide ions = yellow precipitate
How do you confirm the result of the test for halide ions, and what is the result of this ?
- test : add ammonia
- result : white precipitate redissolves ; cream precipitate redissolves in concentrated ammonia ; yellow precipitate does not redissolve
Why is the test for halides a precipitation reaction ?
two aqueous solutions react and a precipitate is formed
