Noble Gases: Properties, Uses, Discovery, and Board Question Practice (SSC)

Published: August 9, 2026

Group 0 or Group 18 elements of the periodic table are collectively known as noble gases, also called inert gases. As of July 2025, seven noble gases have been discovered: Helium, Neon, Argon, Krypton, Xenon, Radon, and Oganesson. This note covers not just definitions and uses, but the reasoning behind why these elements behave the way they do — the part that actually shows up in board exam explanation questions.

Discovery of the Noble Gases

Although Helium sits first in the noble gas group, it was not the first noble gas discovered on Earth. That distinction belongs to Argon, discovered in 1894 by Lord Rayleigh and Sir William Ramsay — a joint effort that earned both scientists Nobel Prizes in 1904 (Rayleigh in Physics, Ramsay in Chemistry).

Helium's story is stranger. It was first detected in 1868, but not on Earth — in the Sun's spectrum, during a solar eclipse. At the time, nobody recognized it as a noble gas at all. It took until 1895 for Sir William Ramsay to isolate Helium on Earth and confirm what it actually was.

💡 Common mistake: Students often assume Helium, being the first element in Group 18, must also be the first noble gas discovered. In reality, Argon was identified and confirmed as a noble gas on Earth before Helium was isolated here — even though Helium was technically detected (in the Sun) decades earlier, in 1868.

Electron Configuration and Position in the Periodic Table

📖 Valence shell / octet: The valence shell is the outermost electron shell of an atom. When this shell holds the maximum number of electrons it can (2 for the first shell, 8 for shells beyond that — following the pattern ns² np⁶), it is called a complete octet, and the atom becomes exceptionally stable.

Why is Helium not placed in Group 2 of the periodic table? Explain.

Textbook reference: p. 69

The electron configuration of Helium is 1s². With 2 electrons in its outermost shell, it might seem to belong in Group 2 alongside the alkaline earth metals — that grouping is based purely on outer-shell electron count. But Helium's outermost shell is completely filled, so it doesn't share the reactivity or metallic character that defines Group 2 elements. Since there's no other meaningful similarity to alkaline earth metals beyond electron count, Helium is placed in Group 0 (Group 18) instead.

Determine the position of Argon in the periodic table.

Textbook reference: p. 67

Electron configuration of Argon, Ar(18) = 1s² 2s² 2p⁶ 3s² 3p⁶

Period: Electrons occupy three energy levels, so Argon belongs to the 3rd period.

Group: The valence shell has s and p orbitals occupied, giving group number = 10 + 6 + 2 = 18.

Argon is therefore located in Period 3, Group 18.

 

Why Are Noble Gases Inert?

Every "explain the inertness of X" board question — regardless of which noble gas is asked about — follows the exact same underlying logic. Once you understand the pattern below, you can answer it for any element in the group.

📖 The core pattern: Every noble gas (except Helium) has the valence shell configuration ns² np⁶ — a complete octet. Helium is the exception with just 1s² (a complete first shell, which only needs 2 electrons). Because the valence shell is already maximally stable, these elements have no tendency to gain, lose, or share electrons — which is exactly what chemical bonding requires. No tendency to bond = inert.

Why are the elements of Group 18 called inert gases?

Uttara High School and College, Dhaka

Textbook reference: p. 74

Elements of Group 18 have the valence shell configuration ns² np⁶ (Helium being the exception). Since the valence shell already holds a complete octet, these elements are extremely stable and have no tendency to donate, accept, or share electrons. Because they cannot form chemical bonds under normal conditions, they are called inert gases.

Why are inert gases not active?

Government P. N. Girls High School, Rajshahi

Textbook reference: p. 74

The electron configuration (...ns² np⁶) shows the outermost shell is octet-complete. As a result, inert gases show no tendency to exchange or share electrons, and cannot chemically combine with other elements — which is why they remain inactive.

Helium is an inert gas — explain.

Mirzapur Cadet College, Tangail Khulna Public College

Textbook reference: p. 74

Helium's electron configuration is He(2) = 1s², meaning its single orbital is completely filled. Since the 1st period has no other orbitals to fill, and the 1s orbital is already full, Helium cannot combine with any other element — not even with another Helium atom. Unable to donate, accept, or share electrons, it qualifies as an inert gas.

Why is 10Ne inert? Explain.

Government P. N. Girls High School, Rajshahi

Textbook reference: p. 74

The electron configuration of 10Ne (1s² 2s² 2p⁶) shows a complete octet in the outermost shell — an exceptionally stable arrangement. Breaking this stability would require a large amount of energy, so Neon does not combine with other elements under normal conditions.

Why is Ar called an inert gas? Explain.

Jalalabad Cantonment Public School and College, Sylhet Milestone College, Dhaka Feni Girls' Cadet College

Textbook reference: p. 74

The valence shell of 18Ar (1s² 2s² 2p⁶ 3s² 3p⁶) holds a complete octet, making it extremely stable. Since a large amount of energy would be needed to disturb this configuration, Argon does not combine with other elements under normal conditions.

Krypton is an inert element — explain.

Textbook reference: p. 74

Kr(36) = 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ — the valence shell holds 8 electrons, a complete octet. Because of this stability, Krypton does not react with other elements under normal conditions.

What is the reason for the inertness of Og?

Cantonment Public School and College, Tangail

Textbook reference: p. 74

Oganesson's valence shell (7s² 7p⁶) is completely filled with electrons. Since it cannot accept, donate, or share electrons, Og is inert.

💡 Common mistake: Students often generalize "noble gases never react" as an absolute rule. At the SSC/HSC level, that's the expected answer — and it's correct for the reasoning above. But it's worth knowing (especially for curious students, or HSC-level extension) that heavier noble gases like Xenon can form compounds (e.g., XeF₂, XeF₄) under special high-energy conditions, because their larger, more distant valence electrons are held less tightly. The octet-stability argument explains why this is rare and difficult — not why it's impossible in every case.

Properties of the Noble Gases

Uses of the Noble Gases

📌 Worth knowing: Radon is radioactive, which sets it apart from the other naturally stable noble gases — it's monitored as an indoor air-quality hazard in some countries rather than put to everyday use. Oganesson is synthetic and so unstable it exists for only a fraction of a second in lab conditions, so its properties are largely theoretical/predicted rather than directly measured.