Group 18 Elements: The noble gases (Group \(18\)), which are found at the far right of the periodic table, were originally known as “inert gases” because of their filled valence shells (octets), which make them exceedingly nonreactive. In comparison to other element groupings, noble gases were discovered comparatively late. Henry Cavendish, who lived in the late \({\rm{1800s,}}\) was the first to discover noble gases. By chemically eliminating all oxygen and nitrogen from a container of air, Cavendish was able to identify these elements.

Helium

Helium was discovered in \(1868\) and appeared as a bright yellow line in the solar spectrum with a wavelength of \(587.49\) nanometers. Pierre Jansen was the one who made this discovery. Jansen assumed it was a sodium line at first. Sir William Ramsay (who extracted helium on Earth by treating a variety of rare elements with acids) later proved that the bright yellow line from his experiment matched that of the sun’s spectrum. From this, British physicist William Crookes identified the element as helium.

Argon

John William Strutt observed in \(1894\) that pure nitrogen synthesised chemically was less dense than nitrogen extracted from air samples. He deduced that another unknown gas was present in the air as a result of this breakthrough. Strutt was able to repeat and adapt Cavendish’s experiment with the help of William Ramsay in order to better comprehend the inert component of air in his original experiment. The researchers used a process that differed from Cavendish’s in that they eliminated the oxygen by reacting it with copper and the nitrogen by reacting it with magnesium. The residual gas was classified accurately, and the new element was given the name “argon,” which comes from the term “inert.”

Neon, Krypton, Xenon

Morris W. Travers and Sir William Ramsay discovered these three noble gases in \(1898.\) By cooling a sample of air to a liquid phase, reheating the liquid, and catching the gases as they boiled off, Ramsay discovered neon. This method also led to the discovery of krypton and xenon.

Radon

Friedrich Earns Dorn discovered the last gas of Group \(18:\) Radon, while examining the decay chain of radium in \(1900.\) Dorn discovered that radium compounds emit radioactive gas during his research. The International Committee for Chemical Elements and the International Union of Pure and Applied Chemistry (IUPAC) chose the name radon for the element in \(1923.\)

Electronic Configurations 

The electronic configurations of group \(18\) elements are given below:

Helium:  \({\rm{1}}{{\rm{s}}^{\rm{2}}}\)

Neon:  \([{\rm{He}}]2\;{{\rm{s}}^2}2{{\rm{p}}^6}\)

Argon:  \({\rm{[Ne]3}}{{\rm{s}}^{\rm{2}}}{\rm{3}}{{\rm{p}}^{\rm{6}}}\)

Krypton:  \([{\rm{Ar}}]3\;{{\rm{d}}^{10}}4\;{{\rm{s}}^2}4{{\rm{p}}^6}\)

Xenon:  \({\rm{[Kr]4}}{{\rm{d}}^{{\rm{10}}}}{\rm{5}}{{\rm{s}}^{\rm{2}}}{\rm{5}}{{\rm{p}}^{\rm{6}}}\)

Radon:  \([{\rm{Xe}}]4{{\rm{f}}^{14}}5\;{{\rm{d}}^{10}}6\;{{\rm{s}}^2}6{{\rm{p}}^6}\)

Atomic and Physical Properties

1. Down a group in the periodic table, atomic mass, boiling temperature, and atomic radii   INCREASE.
2. As you move down the periodic table, the first ionisation energy DECREASES.
3. Because of their chemical inertness, noble gases have the highest ionisation energies.
4. As atomic radius and interatomic tensions decrease in Group \(18,\) melting point, boiling point, enthalpy of vaporisation, and solubility all increase.
5. The INCREASE in atomic mass is associated with the INCREASE in density down the group.
6. As the atomic size of the atoms increases down the group, the electron clouds of these non-polar atoms become more polarised, resulting in weak van der Waals forces between the atoms. As a result of their melting and boiling temperatures, these heavier elements have an easier time forming liquids and solids.
7. Noble gases are exceptionally stable due to their complete outer shells, which prevent them from forming chemical interactions and have a low tendency to gain or lose electrons.
8. All members of the noble gas group behave similarly under ordinary conditions.
9. Under normal conditions, all of the gases are monatomic.
10. Noble gas atoms, like atoms in other groups, have a consistent increase in atomic
    radius from one period to the next as the number of electrons increase.
11. Several features of noble gases are strongly associated with atom size. 
12. Because the valence electrons in bigger noble gases are further away from the nucleus, they are held less securely by the atom, and the ionisation potential DECREASES with increasing radius.
13. As a result of an INCREASE in polarizability and consequently a DECREASE in ionisation
    potential, the attractive force INCREASES with the size of the atom.
14. Overall, noble gases have weak interatomic forces, and therefore very low boiling and melting points compared with elements of other groups.

Applications of Noble Gases

Helium

Because of its limited solubility in fluids and lipids, helium is employed as a component of breathing gases. This is significant because other gases are absorbed by the blood and body tissues when scuba diving under pressure. Helium is taken into cell membranes in small amounts due to its low solubility; when it replaces part of the breathing mixture, helium reduces the narcotic effect of the gas at great depths. Because there is less dissolved gas in the body, fewer gas bubbles occur, lowering the ascending pressure. Welding arcs and the surrounding base metal are shielded from the atmosphere using helium and argon.

Neon

Neon is used in various applications, including neon lights, fog lights, TV cine-scopes, lasers, voltage detectors, luminous warnings, and advertising signs, to name a few. The neon tube used in advertising and ornate decorations is the most common application of neon. Under low pressure, these tubes are filled with neon and helium or argon and subjected to electrical discharges. The colour of the emitted light is determined by the gaseous mixture’s composition and the colour of the tube’s glass.

Argon

Electronics, lighting, glass, and metal fabrications all need argon. Argon is used in electronics to protect ultra-pure silicon crystal semiconductors from heat transfer and to develop germanium. Argon can also be used to create the blue light seen in “neon lamps” by filling fluorescent and incandescent light bulbs with it. Manufacturers of double-pane insulated windows use argon because of its poor thermal conductivity. The energy efficiency of the windows is improved with this insulation barrier.

Krypton

Krypton, like argon, can be found in energy-efficient windows. Krypton is occasionally preferred over argon for insulation because of its better thermal efficiency. According to estimates, krypton is utilised in \(30\% \) of energy-efficient windows supplied in Germany and England; around \(1.8\) litres of krypton is used in these nations. Fuel sources, lasers, and lighting all contain krypton. Krypton serves as a control for a desired optic wavelength in lasers. To make excimer lasers, it’s commonly combined with a halogen (most often fluorine). Krypton-halogen sealed beam headlights have up to twice the light output of ordinary headlights.

Xenon

Xenon is used in incandescent lighting, \({\rm{x – }}\)ray development, plasma display panels (PDPs), and other applications. Xenon is utilised in incandescent lighting because it consumes less energy to produce the same amount of light as a traditional incandescent lamp. Xenon has also improved the quality of \({\rm{x – }}\)rays while reducing the quantity of radiation used. When combined with oxygen, it can improve CT imaging contrast. These applications have greatly impacted the healthcare industry. Plasma display panels (PDPs) that use xenon as one of the fill gases could eventually replace big picture tubes in television and computer screens.

Radon

After cigarette smoking, radon is said to be the second most common cause of lung cancer. Radiotherapy, arthritis treatment, and bathing are just a few of the applications. Radon has been utilised in radiation in the form of implantable seeds made of glass or gold, which are mostly employed to treat malignancies. It has been suggested that radon exposure helps to prevent auto-immune illnesses like arthritis. Some people with arthritis have sought relief from their pain by exposing themselves to radioactive mine water and radon.

Summary

1. The noble gases (Group \(18\)), which are found at the far right of the periodic table, were originally known as “inert gases” because of their filled valence shells (octets), which make them exceedingly nonreactive.
2. Down a group in the periodic table, atomic mass, boiling temperature, and atomic radii  INCREASE.
3. As you move down the periodic table, the first ionisation energy DECREASES.
4. Because of their chemical inertness, noble gases have the highest ionisation energies.
5. Overall, noble gases have weak interatomic forces, and therefore very low boiling and melting points compared with elements of other groups.

FAQs on Group 18 Elements: Noble Gases

Q.1. Why noble gases are known as noble gases?
Ans: The noble gases (Group \(18\)), which are found at the far right of the periodic table, were originally known as “inert gases” because of their filled valence shells (octets), which make them exceedingly nonreactive.

Q.2. What is the electronic configuration of noble gases?
Ans: The electronic configurations of group \(18\) elements are given below:
Helium: \({\rm{1}}{{\rm{s}}^{\rm{2}}}\)
Neon: \([{\rm{He}}]2\;{{\rm{s}}^2}2{{\rm{p}}^6}\)
Argon: \({\rm{[Ne]3}}{{\rm{s}}^{\rm{2}}}{\rm{3}}{{\rm{p}}^{\rm{6}}}\)
Krypton: \([{\rm{Ar}}]3\;{{\rm{d}}^{10}}4\;{{\rm{s}}^2}4{{\rm{p}}^6}\)
Xenon: \({\rm{[Kr]4}}{{\rm{d}}^{{\rm{10}}}}{\rm{5}}{{\rm{s}}^{\rm{2}}}{\rm{5}}{{\rm{p}}^{\rm{6}}}\)
Radon: \([{\rm{Xe}}]4{{\rm{f}}^{14}}5\;{{\rm{d}}^{10}}6\;{{\rm{s}}^2}6{{\rm{p}}^6}\)

Q.3. Why do noble gases have the highest ionisation energies?
Ans: Because of their chemical inertness, noble gases have the highest ionisation energies.

Q.4. What are the applications of neon gas?
Ans: Neon is used in a variety of applications, including neon lights, fog lights, TV cine-scopes, lasers, voltage detectors, luminous warnings, and advertising signs, to name a few.

Q.5. What are the applications of radon gas?
Ans: Radiotherapy, arthritis treatment, and bathing are just a few of the applications. Radon has been utilised in radiation in the form of implantable seeds made of glass or gold, which are mostly employed to treat malignancies.

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