Group 18 Elements (Noble Gases)

Edited By Shivani Poonia | Updated on Jul 02, 2025 07:24 PM IST

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.

This Story also Contains

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

Group 18 Elements (Noble Gases)

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.

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.

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).

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.

Frequently Asked Questions (FAQs)

1. 1. The major Noble Gases in Group 18 are:

Noble gases are basically helium, neon, argon, krypton, xenon, and radon. Noble gases have very low reactivity and variable physical properties.

2. 2. What makes noble gases inert?

Noble gasses can be called inert because their valency shell is full, so they tend not to react or form any chemical bonds under ordinary conditions.

3. 3. What are the common uses of helium?

Some common uses of helium include inflating balloons, cooling superconducting magnets in cryogenics, and using it in different breathing mixtures for patients suffering from respiratory disorders.

4. 4. How do noble gases produce light?

An electric current will make noble gases glow with light due to excited electrons. For each noble gas, its individual characteristic color is produced; for example, neon will produce an orangish-red glow.
A large application for argon is in welding, where it is used to provide an inert atmosphere during the welding operation to prevent oxidation and contamination. This technique is employed to obtain a clean and sound weld.

5. 5. What is the significance of argon in welding?

Argon is significant in welding because it provides an inert atmosphere that protects the weld from oxidation and contamination, ensuring a strong and clean weld.

6. How do noble gases differ from other elements in terms of their boiling and melting points?

Noble gases have extremely low boiling and melting points compared to other elements. This is because they only have weak van der Waals forces between their atoms, rather than stronger covalent or ionic bonds, making it easier to separate them into a gas or liquid state.

7. How do noble gases contribute to the atmosphere?

Noble gases, primarily argon, make up about 1% of Earth's atmosphere. While they don't participate in biological processes, they play a role in maintaining atmospheric pressure and can be used as tracers in studying atmospheric processes.

8. What is the "missing noble gas" and why is it significant?

The "missing noble gas" is element 118, oganesson. It's significant because it completes the 7th period of the periodic table and is the heaviest noble gas. However, its chemical properties are largely unknown due to its extremely short half-life and difficult production.

9. Why is argon used in light bulbs?

Argon is used in light bulbs because it's inert and doesn't react with the hot filament. It also has a lower thermal conductivity than air, which helps maintain the filament's temperature. This inertness and insulating property extend the life of the bulb.

10. Why is helium used in balloons instead of hydrogen, despite hydrogen being lighter?

Helium is used in balloons instead of hydrogen primarily for safety reasons. While hydrogen is lighter, it's highly flammable and can explode if ignited. Helium, being inert, doesn't pose this risk. It's also non-toxic and provides sufficient lift for most applications.

11. What is the electron configuration pattern for noble gases?

Noble gases have a full outer shell of electrons. For helium, this means 2 electrons (1s²). For the rest, it's 8 electrons in the outermost shell (ns² np⁶, where n is the principal quantum number).

12. Why are noble gases generally inert?

Noble gases are generally inert because they have a full outer shell of electrons, which is a very stable configuration. This stability means they don't readily gain, lose, or share electrons, making them unreactive in most conditions.

13. Why are noble gases called "noble"?

Noble gases are called "noble" because they are extremely unreactive, similar to how noble metals like gold are resistant to chemical change. This low reactivity is due to their stable electron configurations, with full outer shells of electrons.

14. How does the reactivity of noble gases change as you move down Group 18?

As you move down Group 18, the reactivity of noble gases slightly increases. This is because the outermost electrons are farther from the nucleus and more easily influenced by other atoms, making heavier noble gases like xenon capable of forming some compounds.

15. Why is neon used in signs?

Neon is used in signs because it produces a bright, distinctive orange-red glow when an electric current passes through it. This property, combined with its chemical inertness and low reactivity, makes it ideal for long-lasting, eye-catching illuminated signs.

16. What are some practical applications of helium?

Helium has several practical applications due to its unique properties:

17. How do noble gases contribute to the field of atomic theory?

Noble gases played a crucial role in developing atomic theory. Their discovery and stable electron configurations helped scientists understand electron shell structure and led to the development of the octet rule, which explains chemical bonding in many compounds.

18. What is the relationship between noble gases and the periodic table's structure?

Noble gases form Group 18 of the periodic table, marking the end of each period. Their stable electron configurations helped scientists understand electron shell filling patterns, which is fundamental to the periodic table's organization and the periodic law.

19. How do noble gases contribute to the study of the universe?

Noble gases are important in cosmology and astrophysics. Their presence and ratios in celestial bodies and atmospheres can provide information about the formation and evolution of planets and stars. They're also used in dating techniques for determining the age of rocks and atmospheric samples.

20. What role do noble gases play in the nuclear industry?

Noble gases play several roles in the nuclear industry:

21. How do noble gases contribute to our understanding of chemical bonding?

Noble gases, particularly the compounds of xenon, have expanded our understanding of chemical bonding. They've shown that even elements with full electron shells can form bonds under certain conditions, leading to concepts like hypervalency and challenging traditional bonding theories.

22. What is the "noble gas trap" in geochemistry?

The "noble gas trap" in geochemistry refers to the ability of certain minerals or rocks to retain noble gases over geological timescales. This property is useful for dating techniques and studying the formation and evolution of the Earth and other planetary bodies.

23. How do noble gases contribute to the field of anesthesiology?

Xenon has been investigated as an anesthetic gas due to its ability to interact with neuronal ion channels. It's non-toxic, non-flammable, and rapidly eliminated from the body. While not widely used due to cost, it demonstrates how even inert gases can have biological effects under certain conditions.

24. What is the "helium problem" in cosmology?

The "helium problem" in cosmology refers to the discrepancy between the observed and predicted amounts of helium in the universe. This problem has implications for our understanding of the Big Bang theory and the early universe, as helium was one of the first elements formed after the Big Bang.

25. What is the role of noble gases in the evolution of stars?

Noble gases play a crucial role in stellar evolution. Helium, produced by hydrogen fusion, is a key player in the life cycle of stars. The production of heavier noble gases through stellar nucleosynthesis provides insight into the processes occurring in stellar interiors and supernovae.

26. How do noble gases contribute to our understanding of Earth's history?

Noble gases, particularly their isotopes, are valuable tools in studying Earth's history. They can be used in radiometric dating of rocks and minerals, tracing atmospheric evolution, and studying processes like mantle degassing. This helps reconstruct Earth's geological and atmospheric past.

27. What is the significance of the discovery of noble gas compounds?

The discovery of noble gas compounds, particularly xenon compounds, was significant because it challenged the long-held belief that noble gases were completely inert. This discovery expanded our understanding of chemical bonding, valence theory, and the periodic table, showing that even "inert" elements can form compounds under certain conditions.

28. How do noble gases contribute to our understanding of nuclear structure?

Noble gases, with their stable electron configurations, have played a role in understanding nuclear structure. The concept of "magic numbers" in nuclear physics, which explain the stability of certain nuclei, was partly developed by observing the patterns in noble gas isotopes.

29. What is the "helium flash" in stellar evolution?

The "helium flash" is a stage in the life of low to intermediate-mass stars when helium fusion suddenly begins in the core. This event, unique to noble gas helium, marks a significant transition in a star's life and demonstrates the crucial role of noble gases in stellar processes.

30. How do noble gases challenge the octet rule?

While noble gases typically follow the octet rule with 8 valence electrons (except helium with 2), some heavier noble gases like xenon can form compounds that exceed the octet, such as XeF4. This challenges the universality of the octet rule and demonstrates its limitations.

31. How do noble gases contribute to our understanding of atomic structure?

Noble gases, with their stable electron configurations, helped scientists understand electron shell structure and energy levels. Their spectra also provided insight into electron transitions and the quantized nature of electron energy levels in atoms.

32. What is the "noble gas core" and why is it important in chemistry?

The "noble gas core" refers to the stable electron configuration of the nearest noble gas in an atom's electron structure. It's important because many elements achieve stability by gaining, losing, or sharing electrons to attain a noble gas-like electron configuration.

33. How do noble gases interact with light, and why is this property useful?

Noble gases interact with light by emitting specific colors when electrically excited. This property is useful in creating colorful neon signs, plasma displays, and in spectroscopy for identifying elements based on their characteristic emission spectra.

34. Why are some noble gases used in welding?

Noble gases like argon and helium are used in welding as shielding gases. Their inert nature prevents the hot metal from reacting with atmospheric gases like oxygen and nitrogen, which could weaken the weld. This results in stronger, cleaner welds.

35. How do the atomic radii of noble gases compare to other elements in the same period?

Noble gases have the largest atomic radii among elements in the same period. This is because they have a full outer electron shell, which exerts a strong repulsive force, pushing the electron cloud outward and increasing the atom's size.

36. What is the significance of radon being radioactive?

Radon's radioactivity is significant because it's a health hazard when it accumulates in buildings. As the only radioactive noble gas found in nature, it challenges the notion that all noble gases are completely safe and inert. Its presence necessitates radon testing in some areas.

37. Why is xenon used in certain types of car headlights?

Xenon is used in high-intensity discharge (HID) car headlights because it produces a bright, white light that closely resembles daylight when electrically excited. This provides better visibility for drivers. Xenon's inertness also ensures a long lifespan for these bulbs.

38. How do noble gases challenge the traditional concept of valency?

Noble gases challenge the traditional concept of valency because they were long thought to be completely inert due to their full outer electron shells. However, the discovery of xenon compounds showed that some noble gases can form bonds and have non-zero valencies under certain conditions.

39. How do noble gases differ in their ability to form compounds?

The ability of noble gases to form compounds increases as you move down the group. Helium and neon don't form any known stable compounds. Argon forms only a few unstable compounds. Krypton can form some compounds under special conditions. Xenon forms several stable compounds, and even some ionic compounds have been reported for radon.

40. Why is argon used in the preservation of historical documents?

Argon is used to preserve historical documents because it's inert and doesn't react with the materials in the documents. It displaces oxygen and moisture, which can cause degradation over time. This inert atmosphere helps prevent decay and extends the life of valuable artifacts.

41. How do noble gases behave under extreme pressures?

Under extreme pressures, noble gases can exhibit unexpected behaviors. For example, helium can become a solid at very high pressures, even at room temperature. Some theoretical studies suggest that under extreme conditions, noble gases might even become metallic or form unusual compounds.

42. Why is krypton used in certain types of lasers?

Krypton is used in certain types of lasers because when electrically excited, it emits a characteristic bright white-blue light. This property makes krypton-based lasers useful in applications requiring high-power, high-precision light sources, such as in scientific research or medical procedures.

43. How do noble gases contribute to our understanding of planetary atmospheres?

Noble gases are important tracers in studying planetary atmospheres. Their abundances and isotopic ratios can provide information about a planet's formation, evolution, and potential loss of atmosphere over time. This has been particularly useful in studying Mars and Venus.

44. Why is neon relatively rare on Earth despite being common in the universe?

Neon is rare on Earth despite being common in the universe because it's a very light gas that wasn't easily retained by Earth's gravity during its formation. Most of Earth's original neon escaped into space, leaving only trace amounts in our atmosphere.

45. How do noble gases interact with other elements at the atomic level?

Noble gases typically interact with other elements through weak van der Waals forces due to their stable electron configurations. However, in compounds like XeF2, xenon can form covalent bonds by sharing its outer electrons. This interaction is possible due to xenon's larger size and more easily influenced outer electrons.

46. What is the significance of helium's superfluidity?

Helium's superfluidity, observed in its isotope helium-4 at very low temperatures, is significant because it represents a quantum state of matter. This property, characterized by zero viscosity and infinite thermal conductivity, has important applications in studying quantum mechanics and low-temperature physics.

47. How do noble gases contribute to the field of radiation detection?

Noble gases, particularly xenon and argon, are used in radiation detectors. When ionizing radiation passes through these gases, it creates ion pairs that can be detected. This property makes noble gas-filled detectors useful in applications ranging from medical imaging to high-energy physics experiments.

48. Why is argon used in the production of titanium and other reactive metals?

Argon is used in the production of titanium and other reactive metals because it creates an inert atmosphere. This prevents the hot, reactive metal from interacting with atmospheric gases like oxygen and nitrogen, which could form unwanted compounds and impurities in the final product.

49. How do noble gases challenge the concept of electronegativity?

Noble gases challenge the concept of electronegativity because they were traditionally thought to have no electronegativity due to their inertness. However, the discovery of xenon compounds has shown that xenon can have a measurable electronegativity, expanding our understanding of this concept.

50. Why is xenon used in ion propulsion systems for spacecraft?

Xenon is used in ion propulsion systems for spacecraft because it's inert (preventing unwanted reactions), has a high atomic mass (providing good thrust), and is easily ionized. These properties make xenon an efficient propellant for long-duration space missions.

51. How do noble gases behave in the presence of strong magnetic fields?

Noble gases, being diamagnetic due to their closed shell electron configurations, are weakly repelled by strong magnetic fields. This property has applications in magnetic levitation experiments and in studying the behavior of materials in extreme conditions.

52. How do noble gases contribute to the field of plasma physics?

Noble gases are important in plasma physics due to their relatively low ionization energies and inert nature. They're used to create and study plasmas in various applications, from plasma displays to fusion research, providing insights into the behavior of matter in this fourth state.

53. Why is argon used in incandescent light bulbs?

Argon is used in incandescent light bulbs because it's inert and doesn't react with the hot tungsten filament. It also has a lower thermal conductivity than air, which helps maintain the filament's high temperature. This extends the life of the bulb and improves its efficiency.

54. How do noble gases contribute to the field of cryogenics?

Noble gases, particularly helium, are crucial in cryogenics. Liquid helium, with its extremely low boiling point, is used to achieve and maintain very low temperatures. This is essential for various applications, from superconducting magnets in MRI machines to certain types of scientific research.

55. Why is the discovery of oganesson (element 118) significant for noble gas chemistry?

The discovery of oganesson, the heaviest known noble gas, is significant because it completes the 7th period of the periodic table. Its extremely short half-life and difficult production mean its chemical properties are largely unknown, potentially challenging our understanding of noble gas behavior and expanding the frontiers of elemental chemistry.