1. Chemistry of Noble Gases
Dr. Gurpreet kaur

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

3. 1962, Bartlett and Lohmann:
demonstrated the great oxidizing strength of PtF6 in producing O2+PtF6-
IP(Xe) ≈ IP(O2)

4. Physical Properties Noble gases
Element
Outer
electronic
configuration
Vander
Wall's
radius (Å)
First IE
(kj mol-1)
m.pt.
(K)
b.pt.
∆Hfux
∆H vap He Ne Ar Kr Xe Rn
1s2
2s2 2p6
3s2 3p6
4s2 4p6
5s2 5p6
6s2 6p6 -
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

5. Why NOBLE GASES are inert in nature?
Chemical Inertness of these gases is due to following reasons:
The atoms have stable completely field electronic shells
They have high ionisation energies
The noble have almost zero electron affinities.
Therefore, they do not have any tendency to gain, lose or 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 Nδ+ and Lδ-
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
XeF2
XeF4
XeF6
not known: XeF8

8. Xenon difluoride , XeF2
XeF2 is best prepared by heating a mixture of xenon and fluorine in molecular ratio of 2:1 at 4000C in a sealed nickel tube. On cooling quickly, a colourless solid XeF2 separated out. Ni
Xe+F2 XeF C

9. Properties
Xenon difluoride is a colourless, crystalline solid which melts at 1290C.
It reacts with hydrogen to give hydrogen fluoride and xenon.
XeF2 + H2 Xe + 2HF
3. It gives substitution reactions with strong protonic acids.
XeF2 + HX FXeX + HF
FXeX + HX XeX2 + HF
Where X= CIO-4 CF3COO-, SO3F- etc.

10. 4. It hydrolyses slowly but completely in
acidic, neutral or alkaline solutions.
2 XeF2 + 2H2O Xe + 4HF + O2
2 XeF2 + 4NaOH Xe + 4NaF + O2 + 2H2O
5. It oxidizes iodine in the presence of BF3
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. XeF4
It is prepared by heating a mixture of xenon and fluorine, in a nickel vassal, at 4000C under pressure of 5-6 atm.
It can also be synthesized by passing an electric discharge through a mixture of xenon and fluorine at -78OC.
Properties:
It is a colorless, crystalline solid, with m.pt c, sublimes readily.
Oxidized by hydrogen to HF at 300 C.
A stronger fluorinating agent than XeF2

12. XeF6
It is prepared by heating xenon with excess of fluorine (in the molar ratio of 1:20) in a nickel vessel at C under pressure of atm.
Xe F XeF6
It can also be obtained by the oxidation of XeF4 with O2F2 under pressure.
XeF O2F c XeF O2

13. 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.
2XeF6+SiO XeOF4 +SiF4
2XeOF4+SiO2 2XeO2F2+SiF4
2XeO2F2+SiO2 2XeO3+SiF4
(explosive)

14. 2 It reacts with fluoride ion acceptors to form adducts.
XeF6+PtF XeOF4+PtF [XeF5]+[PtF6]-
XeF6+SbF XeF6 .SbF [XeF5]+[SbF6]-
XeF6+AsF XeF6.AsF [XeF5]+[AsF6]-

15. XeOF4
(1) Xenon Oxytetraflouride is prepared by partial hydrolysis of xenon hexaflouride
XeF6 + H2O XeOF HF
(2) By the action of XeF6 on silicon dioxide
2XeF SiO XeOF4 + SiF4
Soon as the yellow colour of XeF6 disappears, the contents are immediately quenched with solid CO2 so as to avoid the formation of XeO3

16. Properties
1. It is a colourless compound melting at -46oC.
2 It is reduced by hydrogen to xenon.
XeOF4+3H Xe+H2O+4HF
3 It reacts with water or silica to form another oxyfluoride, XeO2F2, in ;which xenon remains in the same oxidation state. Further reaction gives explosive compound XeO3

17. 4. Action with water: XeOF4 + H2O XeO2F2 + 2HF XeO2F2 + H2O XeO3 + 2HF
2XeOF4 + SiO XeO2F2 + SiF4
2XeO2F2 + SiO XeO SiF4

18. The compound is purified by fractional distillation.
XeO2F2
1. It is prepared by mixing XeO3 and XeOF4 at temperature close to -78OC.
XeO3+XeOF XeO2F2
The compound is purified by fractional distillation.
2. It is also formed when XeOF4 is hydrolyzed or
reacted with silica.
2XeOF4+SiO XeO2F2+SiF4
XeOF4+H2O XeO2F2+ 2HF

19. Properties 1. It is a colourless solid.
2. Its melting point is 30.8OC.
3. It is easily hydrolyzed to give xenon trioxide.
XeO2F2 + H2O XeO HF.

20. XeO3 Xenon trioxide is prepared by the hydrolysis of XeF6 or XeF4
6XeF H2O XeO3 + 4Xe +24HF+3O2
XeF H2O XeO HF
It acts as a powerful oxidizing agent in acidic medium. For
instance, it oxidizes Pu3+ to Pu4+ in the presence of H+ ions.
6Pu+3 + XeO3 + 6H Pu Xe + 3H2O

21. Structure of Some Xenon Compounds
Formula
Name
Oxidn state
Geometry
XeF2
Xenon difluoride +2
Linear
XeF4
Xenon tetra fluoride +4
Square Planar
XeF6
Xenon hexafluoride +6
Distorted octahedron or pentagonal bipyramidal
XeO3
Xenon trioxide
Pyramidal

22. XeO2F2
Xenon dioxy difluoride +6
Trigonal bipyramidal
XeOF4
Xenon oxy tetrafluoride
Square pyramidal
XeO4
Xenon tetra oxide +8
Tetrahedral
XeO3F2
Xenon trioxy difluoride
Ba2[XeO6]-4
Barium perxenate
octahedral

23. Geometrical Shape Xe F ..
XeF2
sp3d
. . F F
XeF sp3d2 Xe F F
. .

24. Geometrical Shape F F F
XeF sp3d3 .. Xe F F F
. .
XeO sp3 xe

25. XeO2F4 sp3d2 XeO2F2 sp3d F . . O O F O O F F F F F Xe Xe F F F F . . O
. . O xe
XeO2F sp3d O F O O F F F F
XeO2F sp3d2 F Xe Xe F F F F
. . O

26. O F F
XeOF sp3d2 Xe F F
. . -4 O O O -4 Xe
XeO sp3d2 O O O