Discuss physical properties and chemical properties of noble gases.

Explanation

(i) Physical Properties : All noble gases are monoatomic. They are colourless, odourless and tasteless.
Noble gases are sparingly soluble in water. They have very low melting and boiling points because the only type of interatomic interaction in these elements is weak dispersion forces. Helium has the lowest boiling point (4.2 K) of any known substance. It has an unusual property of diffusing through most commonly used laboratory materials such as rubber, glass or plastics.
(ii) Chemical Properties : The noble gases in general are least reactive (inert). This is due to following reasons :
(i) Except helium (`Is^2`), the noble gases have completely filled (`ns^2 np^6`) valence shell.
(ii) They have high ionisation enthalpy and high positive electron gain enthalpy.
Neil Bartlett, first observed the reaction of noble gas. He first prepared a red compound `O_(2)^(+)[PtF_(6)]^(-)` . He realised that the first ionisation enthalpy of molecular oxygen (1175 kJ `mol^(-1)`) and that of xenon (1170 kj `mol^(-1)`) is almost identical. He made efforts and prepare same type of red coloured compound of Xe i.e., `Xe^(+)[PtF_(6)]^(-)` by mixing `PtF^6` and Xe. Later , many compounds of xenon with fluorine and oxygen have been synthesized.
The compounds of krypton are fewer. Only the difluoride (`KrF_2`) has been studied in detail. Compounds of radon have not been isolated but only identified (`RnF_2`) by radiotracer technique. No true compounds of Ar, Ne or He are yet known.