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
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
