Helium(He), Neon(Ne),Argon(Ar),Krypton (kr), Xenon (Xe) and Radon (Rn) are Noble Gases. They also called as Rare gases. They are members of group VIII A or zero group.The noble gases are present in atmosphere in small amount about 1%.
The electronic configuration of noble gases are:
Isolation of Noble gases:
The principal commercial source of Ne,Ar,Kr and Xe is air. The noble gases are isolate from air. The noble gases are isolate from air either by fractional distillation or by some chemical method.
Helium is produce as a result of radioactive decay. Its amount in the atmosphere is about 5 ppm. It is isolate from natural gases by liquefaction method α-Particles are doubly ionize helium atom He2+.
Neon is 1/65000th part of the atmosphere. It is isolate by liquefaction of air. In the discharge tube neon glows reddish. Liquid neon has 40 times more refrigeration capacity than liquid helium.
Argon is 1/100th part of the atmosphere. It is obtain by liquefaction of air.It is very inert and does not form any true chemical compound.
Traces of krypton are present in air. It is colourless, Odourless gas.Its spectrum gives green and orange spectral lines. Important compound is krypton difluoride.
Xenon is present in the air to a small extent. Its amount in air is 0.08 ppm. Xenon is obtain by fractional liquefaction of air. The solubility of xenon in water is 110 ml at 20 °C . Its forms fluorides and oxides.
Radon is an α decay product of Radium. Its amount in air is very small.It can be obtain as by product from liquefaction of air. A small amount of Radon is collect from radioactive decay of radium.
226 Ra ⟶ 222Ra + 4He
Physical Properties of noble-Gases:
- All the noble-gase’s ( Except He) are close octets. Due to their close octets the noble gase’s have very high values of ionization energy.
- They have low boiling points. Helium has the lowest boiling point of all known substances.
- Their boiling points increase from top to bottom of group.
- Their solubility in water increases down the group. It is due to the reason that bigger atoms show more polarization in water.
- They have very weak vander waal’s forces among their molecules. The reason is that all of their electrons are pair.
Some Physicals Properties of noble gases are:
Application of Noble Gase’s:
- Helium is use as coolant in nuclear reactors.
- Helium and Neon are use in making gas lasers.
- The helium is fill in weather balloons.
- Helium is use in traffic signal lights.
- Argon and Helium are use for welding and cutting process.
- Sea divers use a mixture of 80% helium and 20% oxygen for breathing.
- Helium and argon are use to create inert atmosphere.
- Argon is use in radio tubes, Fluorescent tubes and electric light bulbs.
- Argon is fill in geiger counter which is use to detect radio activity.
- Xenon is use in bactericidal lamps.
- Radon is use in radiotherapy for cancer.
- Krypton is fill in flash lamps use for high speed photography.
- Radon is use for earthquake prediction.