group 7 (halogens) 4.3
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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
what are the colours of halogen salts?
all colourless (KCl, KBr, Kl)
what is the colour of Cl2?
colourless
what is the colour of Br2?
yellow
what is the colour of I2
brown
halogen displacement reactions are all …
redox reactions