Atomic and Physical Properties of Group 18 Elements: In the long form of the periodic table, the elements are classified into four blocks: \({\rm{s,p,d,}}\) and \({\rm{f,}}\) depending on the subshell into which the last electron enters.

The elements in the s and p blocks of the periodic table are known as representative elements or main group elements. Elements in groups \(1\) and \(2\) are classified as \({\rm{s – }}\)block elements, while elements in groups \(13\) to \(18\) are classified as \({\rm{p – }}\)block elements.In this article, we will learn about the atomic and physical properties of group 18 or Noble Gases, a group in the \({\rm{p – }}\)block.

Group 18 Elements: Noble Gases

Group 18 is placed on the extreme right in the periodic table. There are six elements that include Helium \(\left( {{\rm{He}}} \right){\rm{,}}\) Neon \(\left( {{\rm{Ne}}} \right){\rm{,}}\) Argon \(\left( {{\rm{Ar}}} \right){\rm{,}}\) Krypton \(\left( {{\rm{Kr}}} \right){\rm{,}}\) Xenon \(\left( {{\rm{Xe}}} \right){\rm{,}}\) and Radon \(\left( {{\rm{Rn}}} \right)\) These elements are commonly known as noble gases or inert gases as these elements are chemically inert and do not take part in any reaction.

Occurrence

Noble gases are always found in their state due to their inert nature. Except for radon, all of these gases are atomically present in the atmosphere. Their total percentage in dry air is about \(1\% \) by volume, with Argon \(\left( {0.93} \right)\% \) constituting the majority. It is emitted into the atmosphere primarily as a result of the electron capture of potassium.

Helium is also present in natural gases in amounts ranging from \(2\) to \(7\% .\) Helium and neon are found in trace amounts in radioactive element minerals such as monazite, Clevite, pitchblende, and others. Certain springs’ water contains Helium, Neon, and Argon.

Radon is radioactive and does not exist in its form because it decays so quickly.

Atomic and Physical Properties of Group 18 Elements

Some of the important trends of atomic and physical properties of Group \(18\) elements are given as follows:

Electronic Configuration

Except for Helium, all noble gas atoms have eight electrons in the valence shell. The general electronic configuration of noble gases (with the exception of He) is \({\rm{n}}{{\rm{s}}^{\rm{2}}}{\rm{n}}{{\rm{p}}^{\rm{6}}}{\rm{.}}\) Helium has an electronic configuration of \({\rm{1}}{{\rm{s}}^{\rm{2}}}{\rm{.}}\)

Because these configurations are stable, the noble gases have no tendency to gain or lose electrons and thus do not participate in chemical reactions.

Existence

All noble gases are monoatomic, colourless, and odourless gases. The monoatomic state of these gases is caused by the atoms’ stable electronic configuration. As a result, they are incapable of even combining with one another.

Atomic Radii

Moving down the group with an increasing atomic number, it causes the atomic radii to increase. This is due to the addition of another shell at each progressive element on moving down the group.

Ionisation Enthalpies

Noble gases have extremely high ionisation enthalpies. This is due to noble gases’ stable, completely filled electronic configuration. However, the ionisation enthalpies decrease as the atomic number increases from He to Rn due to increasing atomic size.

Electron Gain Enthalpies

Noble gases have no tendency to accept additional electrons due to their stable electronic configurations; thus, their electron gain enthalpies are zero or have large positive values.

Melting and Boiling Points

Noble gases have very low melting and boiling points in comparison to other substances with comparable atomic and molecular masses. This means that only weak van der Waals forces exist between the atoms of noble gases in liquid or solid form.

The van der Waal forces increase as the atomic size of the atom increases, and thus the boiling and melting points increase from He to Rn. Helium has the lowest boiling point of any substance known.

Ease of Liquefaction

The noble gases are difficult to liquefy. This is due to the fact that the only forces holding atoms together are weak van der Waals forces. The ease of liquefaction increases as one moves down the group from He to Rn.

Solubility

These elements are slightly soluble in water, and in general, the solubility increases on moving don the group.

Below given is the table that summarises the physical properties of Group 18 elements.

Uses of Group 18 Elements

Helium

1. Helium is used in the filling of air balloons and aircraft. This is due to the fact that it is flammable and has a very low density. We use fluid Helium as a cryogenic agent to perform tests at extremely low temperatures because it has a very low boiling point of only \({\rm{4}}{\rm{.2}}\,{\rm{K}}{\rm{.}}\)
2. Liquid Helium is commonly used in the cryoscopy process required for superconductivity. Fluid helium is frequently used to cool superconducting magnets in atomic magnetic resonance spectrometers.
3. It is also used as a cooling gas in gas-cooled atomic reactors as well as a streaming gas in gas-fluid chromatography.
4. It is also an important component of the oxygen cylinders used in deep-sea diving.

Neon

1. Neon lights in reddish-orange hues are used to create advertising signs. It is also used in these types of lights when many other gases are required to produce lights of various colours.
2. Neon can also be found in lightning arrestors, high-voltage indicators, television tubes, and metre tubes.
3. Neon and Helium are used to create gas lasers.
4. In many types of gas-filled electron tubes, neon is used singly or in mixtures with other gases in the electronics industry.
5. Because Helium is less soluble in blood than nitrogen at high pressure, marine divers use a mixture of Helium and neon for breathing in the sea.

Argon

1. Argon is used in incandescent light bulbs to prevent the filament from oxidising too quickly. This extends the bulb’s life.
2. Argon is widely used in the welding and casting industries, particularly in the production of specialty alloys and titanium. During arc welding, it is also used as a shielding gas.
3. Argon can be used as a carrier gas in filmmaking.
4. It provides a blanket atmosphere for crystal growth (and, for example, in viniculture). This noble gas is also used in cryosurgery, refrigeration, fire extinguishing, spectroscopy, and airbag inflation.
5. Argon is frequently used as a liquid target for neutrino experiments and direct searches for dark matter.

Krypton

1. It is used in a variety of electric and fluorescent lamps, as well as in a flashlamp used in high-speed photography.
2. They could even react with fluorine, a highly reactive gas.

Xenon

1. It is used in Xenon flash lamps, which are flash lamps.
2. It’s also used in stroboscopic lights and photographic flashes.
3. Lasers are created with the assistance of Xe gas.
4. The element Xe is a natural anaesthetic.
5. Inhaling a mixture of oxygen and Xenon produces a hormone that aids in the production of Red Blood Cells (RBCs).
6. It is used to measure blood flow and to image the brain, heart, and lungs.
7. The element is also used in NMR spectroscopy.

Summary

In this article, we studied that there are six elements present in group \(18\) that have a general electronic configuration of \({\rm{n}}{{\rm{s}}^{\rm{2}}}{\rm{n}}{{\rm{p}}^{\rm{6}}}{\rm{.}}\) We also studied the following points:

1. The atomic number, mass number, atomic radii as well as melting and boiling point increase on moving down the group from He to Rn.
2. The ionization enthalpies decrease on moving down the group from He to Rn.
3. Noble gases are all monoatomic, colourless, and odourless gases.

FAQs

Q.1. What are the atomic and physical properties of Group 18 elements?
Ans: Some of the atomic and physical properties of group \(18\) are as follows:
The atomic radii increase on moving down the group.
The ionization enthalpies of the elements decrease on moving down the group.
The electron gain enthalpy is zero for Group 18 elements as they have a completely filled shell.
The melting and boiling points increase as the atomic size increases from fluorine to astatine.
All the elements of this group exist as gases.

Q.2. What is the atomicity of Group 18 elements?
Ans: Noble gases are chemically inert compounds. They exist as monoatomic gases under normal conditions. As a result, the atomicity of noble gases is \(1.\)

Q.3. What is special about Group 18 elements?
Ans: The specialty of group \(18\) elements is that under standard conditions, all these gases have the same properties: they are all odourless, colourless, monatomic gases with very low chemical reactivity.

Q.4. Are Group 18 elements reactive? Why?
Ans: Noble gases are nonmetallic, non-reactive elements in Periodic Table Group \(18.\) Noble gases have the lowest reactivity of any element. This is due to the fact that they have eight valence electrons, which fill their outer energy level.

Q.5. What are Group 18 elements called?
Ans: The Group \(18\) elements are commonly known by the name Noble gases. This is because these elements are non-reactive as they have their outermost orbit completely filled.

Q.6. Name the elements of Group 18?
Ans: Group \(18\) is placed on the extreme right in the periodic table. There are six elements that include Helium \(\left( {{\rm{He}}} \right){\rm{,}}\) Neon \(\left( {{\rm{Ne}}} \right){\rm{,}}\) Argon \(\left( {{\rm{Ar}}} \right){\rm{,}}\) Krypton \(\left( {{\rm{Kr}}} \right){\rm{,}}\) Xenon \(\left( {{\rm{Xe}}} \right){\rm{,}}\) and Radon \(\left( {{\rm{Rn}}} \right)\)

Learn About Periodic Classification of Elements

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