What Is Noble Gases? | Properties, Electronic configuration, Occurrence |

What Is Noble Gases?
What Is Noble Gases?

The elements like helium (He), neon (Ne), argon (Ar), krypton (kr), xeon (Xe) and radon (Rn) which are placed in zero group of the periodic table are called noble gases. They are also known as rare gases or inert gases. Actually, they are chemically inert and are present in a very small quantity in our atmosphere.

Noble Gases Properties.


Physical Properties of Noble Gases.

Colour and odour:

All gases are colourless and odourless.

Reactivity:

They are chemically inert.

Application of high voltage:

When these gases are subjected to high voltage, they give different colours in the spectra.

  1. Ne glows reddish and its discharge is most intense at ordinary voltage and current.
  2. Kr has brilliant green and orange spectral lines.
Availability:

Xe is available commercially in cylinders at high pressures.

Melting point and boiling point.
Their M.P. and B. P. go on increasing from upper to the downward direction.The reason is increasing polarizabilities and increasing London dispersion forces.
Ionization Energies:
Their ionization energies decrease down the group. This is due to
increasing number of shells and increasing shielding effect.
Solubility In Water:
They are least soluble in water. Xe is slightly soluble in waiter, to the extract of 110 mL dm-3 at 20°C. Anyhow, the solubilities increase down the group.This is due to the reason that big sized atoms are more readily polarized by tho  water molecule.

Heat of vaporization:
They are all gases at ordinary temperature and pressure and so their heats of vaporization increase down the group.This is due to the increasing sizes and increasing polarizabilities.

Electronic Configuration of noble gases.

Electronic Configuration of noble gases.

Except He, all the noble gases have eight electrons in the outermost shells. Their octet is complete. That is why, they have little tendency to do the chemical reactions.

Occurrence of Noble Gases.

Air as one of the sources of the noble gases:
Noble gases occur as minor constituents of our atmosphere. They are approximately one percent.
Noble gases are isolated from the air by using:
  1. Fractional distillation
  2. Chemical methods
Helium (He):
In 1868, Helium was detected in chromosphere of sun. During the total solar eclipse, it was named helium, which was derived from Greek word "Heilos" Which means sun. After hydrogen it is the second most abundant element in the universe.
The helium which is present in the earth is due to emission of the radioactive substances. They are double ionized helium ions.
Isolation of He:
It is simple and economical to isolate the He gas from some neutral gases by liquefaction method.
Neon (Ne):
Neon is also obtained from the liquefaction of the air. It is 1/65000th part of the atmosphere.
Argon (Ar):
Argon was discovered by Ramsay. It was obtained as a by-product from the liquefaction of the air.

Krypton (Kr):
Kr is also present in air to the extent of one ppm.
Xeon (xe):
It is obtained as by-product from the liquefaction and separation of air components. It is present in atmosphere to a very small extent i.e., 0.08 ppm.
Radon (Rn):
Rn is present to a very small extent in the air and it can be obtained as a by-product from the liquefaction of air.
Rn is a α-decay product of Ra. Small quantities of this gas can be collected from radioactive decay of radium isotopes.

Application of Noble Gases.

Uses Of Helium.

  1. In the Treatment of asthma by mixing with oxygen.
  2. For filling weather balloons and airships.
  3. For producing low temperature in research work.
  4. In the preservation of food.
  5. For producing inert atmosphere in welding and certain metallurgical operations.
  6. As a shielding gas for arc welding.
  7. In measuring low temperature in gas thermometry.
  8. Used in single light.
  9. Used in atomic reactors. This is due to the reason that helium has high thermal conductivity, low viscosity and inert nature.

Uses of neon.

  1. In making neon advertising signs, Actually neon lights are visible from long distances and even visible in fog and mist.
  2. In high voltage indicator and T.V. tubes, in voltage stabilizers and current rectifiers.
  3. In making glass lasers.

Uses of argon.

Argon is used:
  1. For filling the electrical bulbs to increase the life of filament. It is mixed with 15% N2.
  2. Used in Geiger counters, which are employed to detect the radioactivity.
  3. Used for producing inert atmosphere in welding and metallurgy of certain metals.
  4. For the filling of fluorcent tubes and radio valves.
  5. By mixing with neon in neon signs, the light of varying colour can be obtained.

Uses of Krypton.

Krypton is used:
  1. To fill fluorscent tubes.
  2. In flash lamps for high speed photography.
  3. Kr85 is used for the measurement of the thickness of the sheets of the metal and plants.

Uses of Xenon:

Xenon is used:
  1. In bactericidal lamp.
  2. In atomic energy field in bubble chamber. In bubble chamber liquid Xe is used for the detection of gamma-photons and neutral mesons.

Uses of radon:

Radon is used:
  1. In radiotherapy of cancer.
  2. For earthquake predications.
  3. For the preparation of ointment for the treatment of cancer and other diseases.
  4. For photography the interior of opaque materials.
What Is Noble Gases? | Properties, Electronic configuration, Occurrence | What Is Noble Gases? | Properties, Electronic configuration, Occurrence | Reviewed by Genuine Chemistry on June 20, 2019 Rating: 5

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