Question

Give reasons for the following:
Noble gases form compounds with fluorine and oxygen only.

Answer 1

Hint: Oxygen and fluorine are more electronegative elements. They are strong oxidizing agents. They can easily attract the lone pair of noble gas elements. This establishes a strong interaction between the oxygen or fluorine and the noble element.

Complete Solution :
The noble gases have filled $\text{ n}{{\text{s}}^{\text{2}}}\text{n}{{\text{p}}^{\text{6 }}}$ electronic configuration in their valence shell. They have very high ionization energies and the electron affinities of noble gases are almost zero or large and positive.
Therefore, noble gases have neither tendency to gain nor to lose any electrons and do not enter into chemical combinations.
- In March 1962, Neil Bartlett noticed that platinum hexafluoride $\text{ Pt}{{\text{F}}_{\text{6 }}}$ is a powerful oxidizing agent that combines with molecular oxygen to form a red ionic compound, dioxygenyl hexaplatinate (V), \[\text{ }{{\text{O}}_{\text{2}}}^{\text{+}}{{\left[ \text{ Pt}{{\text{F}}_{\text{6 }}} \right]}^{-}}\text{ }\] .
-$\text{ }{{\text{O}}_{\text{2}}}(g)+\text{ Pt}{{\text{F}}_{\text{6 }}}(g)\to \text{ }{{\text{O}}_{\text{2}}}^{\text{+}}{{\left[ \text{ Pt}{{\text{F}}_{\text{6 }}} \right]}^{-}}\text{ }$
- This indicates that $\text{ Pt}{{\text{F}}_{\text{6 }}}$ has oxidized $\text{ }{{\text{O}}_{\text{2 }}}$ to $\text{ }{{\text{O}}_{\text{2 }}}^{+}$. Oxygen and xenon have some similarities. The similarities are as listed below,
(i) The first ionization energy of xenon gas $\text{ }\left( 1170\text{ kJ mo}{{\text{l}}^{-1}} \right)\text{ }$ is fairly close to that of oxygen $\text{ }\left( 1175\text{ kJ mo}{{\text{l}}^{-1}} \right)\text{ }$.
(ii) The molecular diameter of oxygen and the atomic radius of xenon are similar.
On this assumption, Bartlett reacted xenon and platinum hexafluoride in the gas phase and an orange-yellow solid of the composition $\text{ XePt}{{\text{F}}_{\text{6 }}}$ was obtained.
$\text{ Xe}(g)+\text{ Pt}{{\text{F}}_{\text{6 }}}(g)\to \text{ X}{{\text{e}}^{\text{+}}}{{\left[ \text{ Pt}{{\text{F}}_{\text{6 }}} \right]}^{-}}\text{ }$
- This confirms that xenon and other noble gases can form compounds with oxygen and fluorine. Oxygen and fluorine are very electronegative elements. They can strongly attract the lone pair of electrons from$\text{ Xe }$. They are a strong oxidizing agent. The noble gas elements do not react with other elements as they are less electronegative and unable to attract the lone pair of electrons from noble elements. Some of the examples of noble gas compounds are $\text{ Xe}{{\text{F}}_{\text{2}}}\text{ }$ , $\text{ Xe}{{\text{F}}_{4}}\text{ }$,$\text{ Xe}{{\text{F}}_{6}}\text{ }$, $\text{ Xe}{{\text{O}}_{3}}\text{ }$,$\text{ XeO}{{\text{F}}_{\text{2}}}\text{ }$ etc.
Due to this, the noble gases form compounds with fluorine and oxygen only.

Note: Note that, number of xenon compounds have been synthesized. The compound of krypton is fewer. Only the difluoride of krypton $\text{ Kr}{{\text{F}}_{\text{2}}}\text{ }$ has been studied. The compounds of radon have not been isolated but only identified $\text{ Rn}{{\text{F}}_{\text{2}}}\text{ }$ .