group 7 (halogens) 4.3 Flashcards
what are halogens?
group 7 elements
covalently bonded
simple molecular substance
what are the three trends of halogens?
all diatonic
colours get darker down the group
MP/BP increases down group
what’s the colour change as you go down the group?
F2 -very pale yellow
Cl2 -pale green
Br -brown
I2 -dark grey
At2 -black
do halogens get more or less reactive down the group?
less reactive as they go down the group:
need to gain an electron
- atoms have more electron shells
- the extra electron is further from the nucleus
- it’s attraction to the nucleus is weaker
what’s the chemical test for chlorine?
damp blue litmus paper > turns white
as chlorine acts as a bleaching agent, removing colour from the paper
what are the group 7 elements?
fluorine, chlorine, bromine, iodine, astatine
what does bromine release?
volatile, brown fumes
what happens to iodine?
sublimes, releases purple fumes
what happens when you react metals with halogens?
forms ionic compound, outer-shell electrons are transferred to the halogen
for example
sodium + chlorine > sodium chloride
what type of reaction is a metal with a halogen?
redox reaction
metal loses electrons and is oxidised
halogen gains election and is reduced
halogen> halide
what’s the formation of hydrogen chloride?
hydrogen(g) + chlorine(g) (green) > hydrogen chloride(g) (colourless)
hydrogen chloride HCL is covalently bonded, simple molecular substance, gas due to a low BP and weak IMFs
how many effects does dissolving hydrogen have (depending on the solvent)?
2
water and methylbenzene
what happens when you dissolve HCl in water?
HCl (g) dissolves to make HCl (aq)
HCl(aq) dissociates to form H+(aq) - which is acidic
forming HCl(aq) called hydrochloric acid
what happens when you dissolve HCl in methylbenzene?
HCl(g) dissolves to form HCl(org)
HCl(org) cannot dissociate
no H+(org)
HCl(org) not acidic
what is halogen displacement reactions?
when a more reactive halogen displaces a less reactive halogen from their compounds
for example:
chlorine(aq) (colourless) + potassium bromide(aq) > bromine(aq) (yellow) + potassium chloride
chlorine displaces bromine as chlorine is more reactive than bromine
