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Group 18 consists of noble gases (He, Ne, Ar, Kr, Xe, Rn, and sometimes Og) characterized by very low reactivity due to full valence electron shells.
Group 18 of the periodic table is the noble gases: helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), radon (Rn), and (historically/optionally) oganesson (Og). Under standard conditions, the first six are odorless, colorless, monatomic gases with very low chemical reactivity and cryogenic boiling points. Their “inertness” comes from having a full valence electron shell, which makes them energetically unlikely to gain, lose, or share electrons; only a few hundred noble-gas compounds are known, and helium and neon form essentially no neutral compounds under normal conditions. Physically, noble gases have weak intermolecular (London dispersion/van der Waals) forces, leading to low melting/boiling points that increase down the group. They also show systematic trends in properties such as atomic radius, ionization energy, and solubility, and they are nearly ideal gases under standard conditions. Chemically, their electron configurations follow a pattern with full outer shells (He: 2; others: 8 valence electrons), which explains their stability and the “noble gas notation” used to write electron configurations compactly. Oganesson’s chemistry and physical state are uncertain due to its extreme instability and relativistic effects. In applications and Earth sciences, noble gases are valuable because they resist reactions and can be traced via isotopic signatures. Industrially, they are used for shielding (argon), buoyancy (helium), and refrigeration (helium/neon), while radon is used in radiotherapy. In geology, isotopic ratios of noble gases (e.g., helium, neon, argon, krypton, xenon) help reconstruct Earth’s degassing history and distinguish sources across geological reservoirs; careful sampling and high-precision mass spectrometry are required to avoid atmospheric contamination and resolve closely spaced isotopes.
Group 18 consists of noble gases (He, Ne, Ar, Kr, Xe, Rn, and sometimes Og) characterized by very low reactivity due to full valence electron shells.
Their weak intermolecular forces produce low boiling/melting points that increase down the group, and their electron configurations explain both chemical inertness and the noble-gas shorthand notation.
Noble gases are widely used in industry and, in Earth sciences, their isotopic ratios act as geochemical tracers of degassing and source heterogeneity, requiring careful sampling and high-precision mass spectrometry.
The periodic-table group containing the noble gases, whose members have full valence electron shells and are typically very unreactive.
Chemically low-reactivity elements (He, Ne, Ar, Kr, Xe, Rn, and sometimes Og) that exist as monatomic gases under standard conditions and have full valence shells.
The outermost electron shell of an atom; in noble gases it is full, making electron exchange or bonding energetically unfavorable.
A weak intermolecular attraction arising from temporary dipoles, which dominates noble-gas interactions and explains their low boiling points.
A shorthand for electron configurations that uses the preceding noble gas as a reference to write the remaining valence electrons more compactly.
The use of isotopic abundances and ratios (e.g., of He, Ne, Ar, Kr, Xe) to trace processes such as Earth’s degassing history and reservoir mixing.
An evacuated glass container with a stopcock used to sample and store noble gases from natural sources while minimizing contamination.
A mass spectrometry approach that can detect multiple isotopes simultaneously, improving sensitivity and throughput for noble-gas isotope analysis.
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