Group 18 elements, their compounds and Structures.ppt

This ppt describes the chemistry of group 18 elements.

1. Chemistry of Noble Gases
Dr. Gurpreet kaur

2. History of Noble Gas CompoundsHistory of Noble Gas Compounds
Before 1962:Before 1962:
• all noble gases are inertall noble gases are inert
• weakly bonded speciesweakly bonded species
• gaseous cationic species: diatomic molecules between gaseous cationic species: diatomic molecules between
noble gas atoms or other atoms (H, O, N, Hg)noble gas atoms or other atoms (H, O, N, Hg)
• very short lifetimesvery short lifetimes

3. 1962, Bartlett and Lohmann:
• demonstrated the great oxidizing strength of PtF
6
in producing
O
2
+
PtF
6
-
•

IP(Xe) ≈ IP(O
2)
Xe + PtF
6 XePtF
6 + Xe(PtF
6)
2
RT
- dependent on reactant ratio
- red-tinged yellow solid

4. Element Outer
electronic
configuration
Vander
Wall's
radius
(Å)
First
IE
(kj mol
-1
)
m.pt.
(K)
b.pt.
(K)
∆H
fux
(kj mol
-1
)
∆H
vap

(kj mol
-1
)
He
Ne
Ar
Kr
Xe
Rn
1s
2
2s
2
2p
6
3s
2
3p
6
4s
2
4p
6
5s
2
5p
6
6s
2
6p
6
-
1.31
1.74
1.89
2.10
2.15
2372
2080
1519
1351
1170
1037
-
24.4
83.6
116
161
200
4.2
27.1
87.3
120
166
211
0.02
0.33
1.18
1.64
2.3
2.9
0.08
1.77
6.5
9.0
12.6
16.4
Physical Properties Noble gases

5. Why NOBLE GASES are inert in nature?
Chemical Inertness of these gases is due to following Chemical Inertness of these gases is due to following
reasons:reasons:
1.1.The atoms have stable completely field electronic shellsThe atoms have stable completely field electronic shells
2.2.They have high ionisation energies They have high ionisation energies
3.3.The noble have almost zero electron affinities. The noble have almost zero electron affinities.
Therefore, they do not have any tendency to gain, lose or Therefore, they do not have any tendency to gain, lose or
share electrons with other atoms. share electrons with other atoms.

6. Energy Considerations
•Why Fluorine?
–Noble gas will remain bound to ligand if it is so
electronegative that energy required to remove electron from
NG is compensated for by the electron acquisition of the
ligand and the electrostatic attraction energy of N
δ+
and L
δ-
•The atoms of chlorine and other halogens are much larger than
fluorine, so attraction energy for (LN)
+
L
-
ion pair is much less.
•In oxides, ionization energy is mostly compensated for by the
electrostatic attraction term (though oxygen atom electron affinity
also contributes).
– Thus only fluorine is stable ligand

7. Compounds of noble gases
•Xenon Fluorides
• readily prepared from the elements
• thermodynamically stable
•XeF
2
•XeF
4
•XeF
6
• not known: XeF
8

8. Xenon difluoride , XeF
2
XeF
2
is best prepared by heating a mixture of xenon and fluorine
in molecular ratio of 2:1 at 400
0
C in a sealed nickel tube. On
cooling quickly, a colourless solid XeF
2 separated out.
Ni
Xe+F
2
XeF
2
400
0
C

9. Properties
1.Xenon difluoride is a colourless, crystalline solid which
melts at 129
0
C.
2.It reacts with hydrogen to give hydrogen fluoride and
xenon.
XeF
2 + H
2 Xe + 2HF
3.3.It gives substitution reactions with strong protonic acids.
XeF
2 + HX
FXeX + HF
FXeX + HX XeX
2 + HF
Where X= CIO
-
4 CF
3COO
-
, SO
3F
-
etc.

10. 4. It hydrolyses slowly but completely in
acidic, neutral or alkaline solutions.
2 XeF
2 + 2H
2O 2 Xe + 4HF + O
2
2 XeF
2 + 4NaOH 2Xe + 4NaF + O
2 + 2H
2O
5.It oxidizes iodine in the presence of BF
3

to give IF.
6. It is a mild fluorinating agent. It reacts with
benzene to give fluorobenzene.
7. It is also a strong oxidising agent.

11. XeF
4
It is prepared by heating a mixture of xenon and fluorine, in a nickel
vassal, at 400
0
C under pressure of 5-6 atm.
It can also be synthesized by passing an electric discharge through a
mixture of xenon and fluorine at -78
O
C.

Properties:
It is a colorless, crystalline solid, with m.pt. 117. 1
0
c, sublimes
readily.
Oxidized by hydrogen to HF at 30
0
C.
A stronger fluorinating agent than XeF
2

12. XeF
6
1.It is prepared by heating xenon with excess of fluorine (in the
molar ratio of 1:20) in a nickel vessel at 250-300
0
C under pressure
of 50-60 atm.
Xe + 3F
2 XeF
6
2.It can also be obtained by the oxidation of XeF
4
with O
2
F
2
under
pressure.
XeF
4 + O
2F
2 -130
0
c XeF
6 + O
2

13. 2XeF
6
+SiO
2
2XeOF
4
+SiF
4
2XeOF
4
+SiO
2
2XeO
2
F
2
+SiF
4
2XeO
2F
2+SiO
2 2XeO
3+SiF
4
(explosive)
Why xenon hexafluorides cannot be stored in glass or silica vessels?
Xenon hexafluoride is extremely reactive. It cannot be stored in
glass or quartz vessels because it reacts with silica of the glass and
give the dangerously explosive xenon trioxide.

14. 2It reacts with fluoride ion acceptors to form adducts.
XeF
6
+PtF
5
XeOF
4
+PtF
5
[XeF
5
]
+
[PtF
6
]
-

XeF
6+SbF
5 XeF
6 .SbF
5 [XeF
5]
+
[SbF
6]
-

XeF
6+AsF
5 XeF
6.AsF
5 [XeF
5]
+
[AsF
6]
-

15. XeOF
4
(1) Xenon Oxytetraflouride is prepared by partial hydrolysis
of xenon hexaflouride
XeF
6
+
H
2O XeOF
4 + 2 HF
(2) By the action of XeF
6 on silicon dioxide
2XeF
6
+
SiO
2
XeOF
4
+ SiF
4
Soon as the yellow colour of XeF
6 disappears, the contents
are immediately quenched with solid CO
2 so as to avoid
the formation of XeO
3

16. Properties
1.It is a colourless compound melting at -46
o
C.
2 It is reduced by hydrogen to xenon.
XeOF
4+3H
2 Xe+H
2O+4HF
3 It reacts with water or silica to form another oxyfluoride,
XeO
2
F
2
, in ;which xenon remains in the same oxidation
state. Further reaction gives explosive compound XeO
3

17. 4. Action with water:
XeOF
4 + H
2O
XeO
2F
2 + 2HF
XeO
2F
2 + H
2O
XeO
3 + 2HF
2XeOF
4 + SiO
2 2 XeO
2F
2 + SiF
4
2XeO
2
F
2
+ SiO
2
2 XeO
3
+ SiF
4

18. XeO
2F
2
1. It is prepared by mixing XeO
3 and XeOF
4 at temperature
close to -78
O
C.
XeO
3+XeOF
4 2XeO
2F
2

The compound is purified by fractional distillation.
2. It is also formed when XeOF
4 is hydrolyzed or
reacted with silica.
2XeOF
4
+SiO
2
2XeO
2
F
2
+SiF
4

XeOF
4
+H
2
O

XeO
2
F
2
+ 2HF

19. Properties
1. It is a colourless solid.
2. Its melting point is 30.8
O
C.
3. It is easily hydrolyzed to give xenon trioxide.
XeO
2F
2 + H
2O
XeO
3 + 2HF.

20. XeO
3

Xenon trioxide is prepared by the hydrolysis of XeF
6
or XeF
4
6XeF
4
+ 12H
2
O

2XeO
3
+ 4Xe +24HF+3O
2
XeF
6
+ 3H
2
O

XeO
3
+ 6HF
It acts as a powerful oxidizing agent in acidic medium. For
instance, it oxidizes Pu
3+
to Pu
4+
in the presence of H
+
ions.
6Pu
+3
+ XeO
3
+ 6H
+

6Pu
+4
+ Xe + 3H
2
O

21. Structure of Some Xenon CompoundsStructure of Some Xenon Compounds
FormulaName Oxid
n

state
Geometry
XeF
2
Xenon
difluoride
+2 Linear
XeF
4
Xenon tetra
fluoride
+4 Square Planar
XeF
6
Xenon
hexafluoride
+6 Distorted octahedron or
pentagonal bipyramidal
XeO
3
Xenon
trioxide
+6
Pyramidal

22. XeO
2F
2 Xenon dioxy
difluoride
+6Trigonal bipyramidal
XeOF
4
Xenon oxy
tetrafluoride
+6Square pyramidal
XeO
4 Xenon tetra
oxide
+8Tetrahedral
XeO
3
F
2
Xenon trioxy
difluoride
+8Trigonal bipyramidal
Ba
2[XeO
6]-4Barium
perxenate
+8octahedral

23. . .
Xe
. .
XeF
4
sp
3
d
2
Xe
F
..
.
.
F
..
Geometrical Shape
XeF
2

F
F
F F
sp
3
d

24. XeF
6
sp
3
d
3
. .
Xe
xe
XeO
3
sp
3
F
F
F
F
F
F
..
Geometrical Shape

25. xe
O
F
O
Xe
F
XeO
2F
2
sp
3
d
O
F F
F
F
.
.
. .
F
XeO
2
F
4
sp
3
d
2 Xe
O
F F
F
F
O

26. XeOF
4
sp
3
d
2
Xe
O
F F
F
O
XeO
6
sp
3
d
2
Xe
O O
O
F
O
-4
-4
O
. .