2.2.3, 2.2.4, 2.2.5: Group 7 Flashcards
Name of group 7
The halogens
Group 7 elements exist as …
diatomic molecules
Group 7 elements are
non - metals
State at room temp of first 4 halogens
F = gas Cl = gas Br = liquid I = solid
Group 7 elements form … ions
halide
Boiling points trend
increase down the group
as elements have more electrons
increase in vdw. and stronger
greater intermolecular force to break
Electronegativity trend
decreases down the group
(as) atomic radius increases
electrons experience less nuclear attraction as further away
Main properties that have trends
3
Boiling points
Electronegativity
Silver halide solubility in NH3
Silver halide solubility in NH3 trend
All silver halides precipitate out of aqueous solution
when ammonia is added, solubility in it decreased down the group
Reactive trends
4
reduction reactions
oxidation reactions
reactions with H2SO4
displacement reactions
Reducing power trend
reduction reactions
Increases down the group
F ions aren’t reducing at all
Causes other ions to gain electrons by donating its own
Oxidising power trend
oxidation reactions
decreases down the group
F is the most oxidising element as its most electronegative
it gains electrons causing other ions to lose them
Reactions with H2SO4
Due to different reducing abilities down the group
HCl or HF
some Br2 and some SO2
I2 immeadiatly reduces S to H2S (toxic smells like eggs)
Displacement reactions
why
If an elemental halide is added to a halide solution = the heavier halide is displaced
(as) the lighter halide is more electronegative
Reactions with silver nitrate to identify halides
Ag + X > AgX precipitate formed AgCl = white AgBr = cream AgI = yellow
Result if ammonia is added to a silver halide
AgCl precipitate will redissolve
AgBr precipitate will redissolve slowly in presence of lots of NH3
AgI won’t redissolve
Disproportionation reaction
An element is oxidised and reduced simultaneously
Reaction of chlorine and water
use and equation
used in water treatment to kill bacteria
Cl2 +H2O = HCl + HClO = 2H+ + ClO- + Cl-
Reaction of chlorine and water in sunlight
same reaction and further reaction
overall reaction: 2Cl2 + 2H2O = 4HCl + O2
Practical uses of chlorine
2
making bleach
adding to the water supply
Making bleach with chlorine
disproportionation reaction
Cl2 + 2NaOH > NaClO + H2O + NaCl
Adding chlorine to the water supply
benefit
risk
+Kills harmful bacteria
- small increased risk of cancer
Chlorine
dangers
3
Cl gas = toxic
Cl liquid = burns eyes and skin
water contains organic trace compounds = chlorine will chlorinate hydrocarbons = carcinogenic
