Group 18 Elements (Noble Gases)

The elements of group 18 are otherwise known as the noble gases of elements. They, however, occupy a rather unique position in the periodic table. The noble gases include helium, neon, argon, krypton, xenon, and radon, in that order. The reason identified is that they have full valence electron shells, hence very nearly inert or non-reactive, which makes them just about the point of difference from the rest of the elements and very much the reason behind their manifold applications in various fields of work. For instance, helium is sufficient not only to inflate balloons but also to use in such areas as cryogenics and medicine, by the factor of safe breathing conditions for people having respiratory illnesses. What makes noble gases even more fascinating is that they are prophesied to be colorless, odorless, and tasteless according to standard conditions.

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This Story also Contains

1. Physical Properties of Group 18 - 1
2. Physical Properties of Group 18 - 2
3. Some Solved Examples
4. Summary

Physical Properties of Group 18 - 1

What explains efficient chemical stability is that noble gases are defined as having a full valence shell.

Noble gases are colorless, odorless, and tasteless at room temperature; thus, efficient chemical stability is observed. All noble gases have different points in atomic numbers that affect their properties: helium, with the most reduced atomic number of 2, gives the lowest points of boiling and melting among noble gases, which makes it lighter than air. As such, neon, argon, krypton, and xenon have boiling points that increase respectively. That aspect can be attributed to changed atomic mass and increased van der Waals forces, so that there goes without saying rather a heavy noble gas and radioactive—the fact that adds further complication to the physical properties of the noble gas. Understanding these properties explains why noble gases are used in very specific applications, which range from lighting to medical technologies.

Electronic Configuration:- noble gases have general electronic configuration ns²np⁶ except helium which has 1s² . Many of the properties of noble gases including their inactive nature are ascribed to their filled orbital configuration.

Ionisation Enthalpy:- Due to stable electronic configuration these gases exhibit very high ionization enthalpy. However, it decreases down the group with an increase in atomic size.

Atomic Radii:- Atomic radii increase down the group with an increase in atomic number.

Electron Gain Enthalpy:- Since noble gases have stable electronic configurations, they have no tendency to accept the electron and therefore, have large positive values of electron gain enthalpy.

Solubility:- Noble gases are slightly soluble in water and their solubility increases down the group from He to Rn with an increase in atomic size.

Electrical conductivity:- These gases have fairly high electrical conductivity. They produce characteristic coloured lights when an electrical discharge is passed through them at low pressure.

Some atomic and physical properties of Noble gases are tabulated below:

Physical Properties of Group 18 - 2

Some even more peculiar optical properties are exhibited by the noble gases.

Their characteristic colors are obtained by passing an electric current through them: neon, a brilliant orange-red; argon, a blue light. But the reason lies at the heart of their application in neon signs and in high-intensity lamps. Noble gases are the largest unreactive; they are used where one needs to have an inert atmosphere. For instance, argon in welding, where the possibility of oxidation has to be avoided, and high-intensity lamps use xenon because it actually is an efficient producer of light. With their high ionization energies, these gases very rarely go through chemical reactions—something useful in special industrial and research applications. => In the end, noble gases are a standard part of every one of these various industries that depend upon the unique qualities of these gases to highlight scientific applications.

Within medicine, Helium is routinely added to respiratory gas mixtures for patients with pulmonary ailments as it reduces work of breathing as it lowers resistance in the airways. Neon is becoming very popular in advertising and promotional uses as it gives off a glowing soft light that is safely touchable. It is also used as an inert gas in filament light bulbs, thus increasing the life of the filament and also that of the bulb. Argon finds its use in the electronics industry during the manufacture of semiconductors where its inertness helps to avoid contamination. It's also done in high-performance flash lamps and as a general anesthetic in medical operations. Uses of radon also apply to the treatment of cancer, although in a radioactive position that indeed provides a source of radiation. Noble gases hence, among others, show applications from the college laboratory into a concrete setting, most relevant at the college level while studying and working in any discipline. That is to say, the elements of this group, which are noble gases, have special physical and chemical properties preferred to them based on their completed valence electron configuration.

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Some Solved Examples

Example 1
Question:
Noble gases are named because of their inertness towards reactivity. Identify an incorrect statement about them.

1) Noble gases are sparingly soluble in water.

2) Noble gases have very high melting and boiling points.

3) Noble gases have weak dispersion forces.

4) Noble gases have large positive values of electron gain enthalpy.

Solution:
Noble gases are usually monoatomic and have very weak interaction forces. They usually have very low melting and boiling points. The stronger the interaction between particles of gas, the higher the boiling and melting points.

Hence, the incorrect statement is option (2).

Example 2
Question:
Which intermolecular force is most responsible for allowing xenon gas to liquefy?

1) Dipole - dipole

2) Ion - dipole

3) Instantaneous dipole - induced dipole

4) Ionic

Solution:
Xenon is a non-polar gas. An instantaneous dipole is created in one Xe molecule, which induces a dipole in another Xe molecule. The instantaneous dipole-induced dipole is the intermolecular force that is most responsible for allowing xenon gas to liquefy.

Hence, the correct answer is option (3).

Example 3
Question:
The compressibility factor for a real gas at high pressure is:

1) $(\mathrm{1 + \frac{RT}{Pb}})$

2) 1

3) $(\mathrm{1 + \frac{Pb}{RT}})$

4) $(\mathrm{1 - \frac{Pb}{RT}})$

Solution:
For real gases, the Van der Waals equation is:

$[( P+\frac{a}{V^{2}})(V-b)=RT]$

At high pressure, $(P\frac{a}{V^{2}})$, so we can neglect $(\frac{a}{V^{2}})$:

$[P(V-b)=RT \quad \text{or} \quad PV=RT+Pb]$

The compressibility factor (Z) is defined as: $=\frac{RT+Pb}{RT}=1+\frac{Pb}{RT}]$

Hence, the correct answer is option (3).

Summary

These gases are colorless and odorless; their typical optical characteristic features establish them as very useful materials in a wide area of applications. From neon, which forms part of advertisements that display colors, to the use of argon in welding, noble gases are variously employed in modern science and technology, thus acting as a key. Knowing these properties and applications does more than just add variations to our knowledge bank in chemistry; it specifically points out the importance of these elements in everyday life.