group 17 (2)
Post on 29-May-2018
216 Views
Preview:
TRANSCRIPT
-
8/9/2019 GROUP 17 (2)
1/39
-
8/9/2019 GROUP 17 (2)
2/39
1. Halogen
2. Reactive non-metallic elements.
Element Chlorine Bromine Iodine
Proton number 17 35 53
Electronic
configuration2.8.7
[Ne] 3s3p2.8.18.7
[ Ar] 4s4p2.8.18.18.7
[Kr] 5s5p
-
8/9/2019 GROUP 17 (2)
3/39
Bottle containingboth liquid and
gaseous bromine Solid
iodine
pieces
Copper
(II)
Fluoride
-
8/9/2019 GROUP 17 (2)
4/39
-
8/9/2019 GROUP 17 (2)
5/39
Group 17, the nuclear charge &
the screening effect .
However, the in screening effect is the in nuclear charge, causing a
in the effecetive nuclear charge.
Hence, the size of the atoms
down the group.
-
8/9/2019 GROUP 17 (2)
6/39
Proton number Element No.ofelectrons/shell
9 fluorine2.7
17 Chlorine 2. 8. 7
35 Bromine2.8. 18. 7
53 Iodine2.8. 18. 18. 7
85 Astatine 2. 8. 18. 32. 18. 7
-
8/9/2019 GROUP 17 (2)
7/39
Element Stateandcolour atroomtemperatureandpressure,colour ofvapour whenheated
Fluorine pale yellow gas
Chlorine pale green gas
Bromine dark red liquid, readily gives off a brown vapour
Iodine dark (~black) crumbly solid, purple vapour
Astatine black solid, dark vapour - highly radioactive!
-
8/9/2019 GROUP 17 (2)
8/39
The smaller the size the higher the
nuclear charge, causing the
attraction of the bond to bestronger.
G 17, the atomic size while the
effective nuclear charge .
Hence, the electronegativity .
-
8/9/2019 GROUP 17 (2)
9/39
The first electron affinity refers to theenthalpy change for the following process:
x(g) + e x(g)
o For example,a) Cl(g) + e Cl(g) H = -364KJ mol
b) I(g) + e I(g) H = -297KJ mol
o Atoms with smaller size and higher
effective nuclear charge will have higheraffinity for the added electrons.
o Hence, the E.A. for the halogens thegroup.
-
8/9/2019 GROUP 17 (2)
10/39
Have a simple molecular structure.
Consist of X molecules with strong covalentbond.
However, the intermolecular forces are theweakvander Waals forces.
G17,the size / no. of electrons .
As a result, the B.P.,M.P. & E.V. as the
molecules become larger & the forces
become stronger.
-
8/9/2019 GROUP 17 (2)
11/39
HalogenStandardAtomic
Weight (u)MeltingPoint (K) BoilingPoint (K)
Electronegativity(Pauling)
Fluorine 18.998 53.53 85.03 3.98
Chlorine 35.453 171.60 239.11 3.16
Bromine 79.904 265.80 332.00 2.96
Iodine 126.904 386.85 457.40 2.66
Astatine (210) 575 610 2.20
-
8/9/2019 GROUP 17 (2)
12/39
halogen molecule structure model
Fluorine F2
Chlorine Cl2
Bromine Br 2
Iodine I2
-
8/9/2019 GROUP 17 (2)
13/39
Bond Cl-Cl Br-Br I-I
Bond
energy/KJ mol
+244 +195 +152
DECREASES
-
8/9/2019 GROUP 17 (2)
14/39
-
8/9/2019 GROUP 17 (2)
15/39
Acts as oxidising agents according to the
equation:
X(aq) + 2e 2X(aq)
Oxidising strength down the group due tothe in size & in the E.A.
Chlorine candisplace( oxidise) bromide and
iodide ion from theiraq. solutions:
a) Cl(g) + 2Br(aq) Br(aq) +2Cl(aq)
b) Cl(g) + 2I(aq) I(aq) + 2Cl(aq)
-
8/9/2019 GROUP 17 (2)
16/39
If the resulting solution is shaken with
tetrachromethane, the bromine liberatedwill colour the organic layer reddish
brown, while iodine will colour it violet.
Bromine can only displace the iodide ions
from its aq. solutions.
Br(aq) + 2I(aq) I(aq) + 2Br(aq)
-
8/9/2019 GROUP 17 (2)
17/39
Produce hydrogen halides (colourless
but form white fumes in moist air)
H(g) +X(g) 2HX(g)
Hydrogen: oxidation state of zero to
+1.
the group, the oxidising power,
hence the reactivity with hydrogen
also.
-
8/9/2019 GROUP 17 (2)
18/39
a) Boiling point and melting point
o M.P. & B.P. In the order HCl
-
8/9/2019 GROUP 17 (2)
19/39
G17, the H-X bonds get weakerdue to the
in the size.Hence, the stabilityof the HXdown the
group.
Bond H-Cl H-Br H-I
Bond
length
0.128 0.141 0.142
Bondenergy/
KJ mol
+430 +370 +300
-
8/9/2019 GROUP 17 (2)
20/39
c) The hydrohalic acids
All the halogen halides dissolved inwater to produce acidic solutions.
HX(g) + HO(l) HO(aq) + X(aq)
As the H-X bonds get weaker downthe group, the degree of dissociation
in water .
Hence, the acid strength in the order
of
HCl
-
8/9/2019 GROUP 17 (2)
21/39
Cl, Br & I react with cold & dilute sodium
hydroxide to form the halide & halate(I) ions.
CI(s) + 2NaOH(aq) NaCI(aq) +
NaOCI(aq)+ HO(l)
Br(s) + 2NaOH(aq) NaBr(aq) +NaOBr(aq)+ HO(l)
I(s) + 2NaOH(aq) NaI(aq) +NaOI(aq)+ HO(l)
-
8/9/2019 GROUP 17 (2)
22/39
With the hot & conc. Sodium
hydroxide, the halogens react to
produce the halate(V) ions. For
example:
3Cl(g) + 6NaOH(aq) 5NaCl(aq) +NaCIO(aq) +3HO(I)
-
8/9/2019 GROUP 17 (2)
23/39
Silver chloride is soluble in both dilute &
conc.ammonia.AgCl(s) + 2NH(aq) [Ag(NH)](aq)+Cl(aq)
Silver bromide is insoluble indilute
ammonia but is soluble in conc.ammonia.
AgBr(s) + 2NH(aq) [Ag(NH)](aq)+Br(aq)
Silver iodide is insoluble in both dilute &conc. aqueous ammonia.
-
8/9/2019 GROUP 17 (2)
24/39
Formed coloured precipitate of silver halide.
Examples: Ag(aq) + Cl(aq) AgCl(s)
white
: Ag(aq) + Br(aq) AgBr(s)
cream
: Ag(aq) + I(aq) AgI(s)
yellow
-
8/9/2019 GROUP 17 (2)
25/39
white fumes of hydrogen halides are
liberated.
E.g : NaCl(s) + HSO(aq) NaHSO(aq) + HCl(g)
However, conc. sulphuric acid is also anoxidising agent, & will further oxidise HBr &
HI to bromine( areddishbrown vapour) &iodine (a violet vapuor) respectively .
2HBr(g) + HSO(aq) Br(g) + 2HO(l) + SO(g)
2HBr(g) + HSO(aq) Br(g) + 2HO(l) + SO(g)
-
8/9/2019 GROUP 17 (2)
26/39
Manganese (IV) oxide is used to
oxidise HCl chlorine.
4NaCl(s)+
4HSO
(aq) + MnO
(aq) Cl(g) + MnCl(aq) 4NaHSO(aq)+ 2HO(l)
-
8/9/2019 GROUP 17 (2)
27/39
-
8/9/2019 GROUP 17 (2)
28/39
Oxidationstate Example
-1 NaCl, HCl
0 Cl
+1 ClO, NaClO
+3 HClO, NaClO
+5 HClO, KClO
+7 KClO, ClO
-
8/9/2019 GROUP 17 (2)
29/39
The oxo-acids of chlorine are:
HOCl,HClO, HClO, HClO
All the oxo-acids dissociate in water:
E.g: HOCl(aq) H(aq) + ClO(aq)
The acid strength depends on the
strength of the O-H bond in themolecule.
Oxygen is more electronegativity than
chlorine, hence the O-H bond in the
oxo-acids are weakened by the oxygenatoms which are bonded to the chlorine
atoms
-
8/9/2019 GROUP 17 (2)
30/39
-
8/9/2019 GROUP 17 (2)
31/39
The electrode process are:
The sodium produced at the cathodecombined with mercury to form unreactivesodium amalgam.
The amalgam is directed into another steeltank where it reacts with water to produce
sodium hydroxide and hydrogen gas.
2Na/Hg(l) + 2HO(l) 2NaOH(aq) + H(g) +2Hg(l)
Anode Cathode
2Cl(aq) Cl(g) + 2e 2Na(aq) + 2e 2Na(l)
Na(l) + Hg(l) Na/Hg(l)
-
8/9/2019 GROUP 17 (2)
32/39
-
8/9/2019 GROUP 17 (2)
33/39
The brine solution enters the cell through
the anode compartment.
The chloride ion is discharged as chlorine gas
at the titanium anode. 2Cl(aq) Cl(g) + 2e
At the steel cathode, hydrogengas is
produced.
2H(aq) + 2e H(g)
Sodium hydroxide together with excess brine
is drainedout from the cell.
-
8/9/2019 GROUP 17 (2)
34/39
-
8/9/2019 GROUP 17 (2)
35/39
-
8/9/2019 GROUP 17 (2)
36/39
1,2- dibromoethane is added to leaded petrol
to remove the lead oxide sticking to the
piston surface.
Silver bromide is used in the manufacture ofpjotographic film.
-
8/9/2019 GROUP 17 (2)
37/39
A solution of iodine in ethanol is a
disinfectant.
Silver bromide is used in photpgraphic film
-
8/9/2019 GROUP 17 (2)
38/39
1. HCl, HBr and HI dissolves in water to form
acidic solutions.
i) Write a balanced equation for the
reactions between hydrogen chloride andwater.
ii) Arrange the three aqueous hydrogen
halides in the order of increasing acid
strength. Explain you answer.
-
8/9/2019 GROUP 17 (2)
39/39
2. Describe the reactions between chlorine,
bromine and iodine with hydrogen.
top related