OCR A Level Salters\\\' Advanced Chemistry Year 2 Student Book (OCR B)
Detailed, concise and organised revision notes summarising the whole of topic 3 of A level Chemistry OCR B (salters advanced). This topic is elements from the sea and includes notes on the halogens, redox reactions, electrolysis, equilibrium, transporting and the benefits of chlorine, iodine-thiosu...
group 7
elements are the halogens
•
all have 7 electrons in their outer shell
•
most reactive of the non metals ,
non found naturally in element form
°
Fluorine and chlorine are the most abundant ,
bromine occurs in smaller quantities ,
iodine and astatine be artificially produced it short tired
is scarce can
only as is
and radioactive .
•
All halogen elements are diatomic molecules .
For example , Fz and Bra
which are linked through a
single coolest bond .
between a pair of atoms .
•
Halogen atoms achieve
stability by gaining an electron →
forming
a halide ion or
sharing an electron with another non metal
Physical properties
element FLUORINE CHLORINE BROMINE IODINE ASTATINE
Formula Fz Uz Br , Iz Asz
appearance at pale yellow pale green dark red volatile
shiny black black
temp liquid → solid → purple vapour solid
room .
gas gas vapour
melting point -2201,53k -1014,172k -7% 1141,387k 3004,573k ,
266k
boiling point -1884,85k -341,239k 591,332k 18401,457k 3401,613h
order
of reactivity I 2 3 4 5
Uses
# ☒ E- ☒ ④ $ -
going down
the
group
-
become darker in colour
melting and boiling point increase
-
-
charge from
gases
→
liquids → solids at room temp .
-
become less volatile
-
electronegativity decreases
, Est
-
CHEMICAL PROPERTIES
-
group of reactive elements , they tend to remove electrons from other elements
so that they can
complete their outer shell e.g .
•
2N a es,
t
Uz egg
→ 2. NaCl is ,
-
Na has lost electron - been oxidised
-
U has gained an electron -
is on
oxidising agent .
-
elements at the top of group 7 are the most reactive and strongest
oxidising agents this decreases down the
,
going group .
The of shell electrons
atom made of it 's nucleus and
•
core an is up inner .
chlorine the outer shell from the and the attraction for
↳ in is
father core
the extra electron is weaker .
Therefore fluorine higher up in the
group ,
,
gains
electrons more readily ,
to become a
negative ion
,
than chlorine
-
Fluorine is the most reactive member of the halogens and the strongest
oxidising agent .
reactions of the halogens with halide ions
if chlorine chemical
-
is added to potassium iodide there is a reaction and
the solution turns brown .
Iodine is produced .
HALF EQUATIONS
Uz Uz 24
-
↳ 2k Clear, Iz 2e
-
can
t 2kt lags → t
caq , t →
↳ Uz Iz 21 Iz 2e
-
- -
21 2cL canst →
-
t → can,
+
can cag ,
↳
half equation ,
ions left out are known as spectator ions
-
each iodide ion loses an electron and is oxidised
each chlorine atom gains an electron i chlorine is the oxidising agent and
-
.
has been reduced
-
if bromine solution is added to iodide ions
:
↳ Bre 21 2B r lzcaas
-
-
t → t
can can can,
Orange lyellow → brown
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