Chemistry OCCURRENCE AND USES OF NOBLE GASES
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OCCURRENCE AND USES OF NOBLE GASES

Occurrence :

These are found in atmosphere to very less extent so named rare gases and form very few compounds so termed noble gases.

`text(Important point)`

All have octet configuration except `He` having duplet configuration.

(i) They exist on gaseous state.

(ii) `Rn` is produced by the disintregration of radium and is radioactive itself.

`text( )_88^(226)Ra ->text( )_86^(222)Rn + text( )_2^4He^(++)`

(iii) Ramsay was the discoverer of these gases.

(iv) First inert gas which was discovered by Ramsay firstly i.e. argon.

(v) All except `Rn` occur in atmosphere almost `1%` by volume in which argon is the major constituent.

Isolation :

Except `He`, non-radioactive noble gases are commercially isolated from air by two method.

(i) `text(Fractional Distillation of Liquid air (Claude's Method) :)`

Due to difference in b.p. the various constituents of air are seprated from each other.

(ii) `text(Dewar's Coconut Chercoal Adsorption Method:)`

(a) `O_2` and `N_2` are removed by means of compound formation.

(b) The principle of this method is that the adsorption capacity of these gases at low temperature by coconut charcoal increases with increases in their atomic weights.

(c) Thus `He` has the lowest and `Xe` has the maximum adsorption capacity.

General Properties :

(i) `text(Atomic Radii, Melting point and Boiling Point, Density :)`

(a) All increases down the group.

(b) `He` is the only element having two boiling point i.e. '4.2 K' and '2.5 K '.

(c) It is `[He]` only element which exist in two liquid phases i.e. `He` and `He_2`.

(d) They are colorless, odourless and tasteless.

(ii) Ionisation Energy :

(a) They possess very high ionisation energy.

(b) Ionisation energy of `Xe` is nearly equal to that of molecular oxygen.

(iii) Electron Affinity :

Due to complete octet, noble gas atoms are unable to take extra electron.

(iv) Monatomicity :

Due to very high `I.E.` and nearly zero `E.A.` noble gas atoms are not capable of combine and their value of `gamm a = C_p/C_v` is close to `1.66.`

(v) `text(Force of attraction between atoms of Noble Gases :)`

Vander Walls force between the atoms increases from `He` to `Xe`.

(vi) `text(Solubility in Water :)` Slightly soluble in water and solubility in water increases with increase in atomic number.

(vii) `text(Chemical Nature :)`

(a) Noble gases are almost chemically inert.

(b) But `Kr`, `Xe` and `Rn` are slightly reactive because of relativly low `IP` of gases.

(viii) `text(Adsorption of lnert Gases :)`

(a) Done on coconut. Gas particles are adsorbed in surface of coconut charcoal

(b) Larger the size, more will be the adsorption so maximum adsorption of `Xe` at highest temp.

(ix) (a) First gas discovered was Argon. (`Ar` gas Lazy)

(b)Other inert gas isolated was Neon.

(c)Other inert gas remaining hidden gas krypton (Kryptos = Hidden)

(d)Then Xenon (Xenon= stranger)

(e) `Rn` emits `alpha`, `beta`, `gamma` radiations.

(f) `He` has unusual property of diffusion through lab material like Rubber, Glass, Plastic.
 
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