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Group 18 contains helium, neon, argon, krypton, xenon, radon, and sometimes oganesson; the first six are typically monatomic, colorless, odorless gases with very low reactivity.
Group 18 of the periodic table is the set of low-reactive (historically “inert”) gases known as the noble gases. Its members are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), radon (Rn), and sometimes oganesson (Og). Under standard conditions, the first six are odorless, colorless, monatomic gases with very low chemical reactivity; oganesson’s properties are uncertain because it is unstable and only a few extremely short-lived atoms have been synthesized. Their low reactivity is explained by electron configuration: the valence shell is “full” (two electrons for helium; eight for the others), making the atoms very stable and unlikely to gain, lose, or share electrons. As a result, noble gases have weak interatomic forces (mainly London dispersion forces), leading to very low melting and boiling points and systematic trends down the group (increasing atomic size and intermolecular attractions). Only a few hundred noble gas compounds are known, with chemistry becoming more feasible for heavier members such as xenon, krypton, and argon.
Group 18 contains helium, neon, argon, krypton, xenon, radon, and sometimes oganesson; the first six are typically monatomic, colorless, odorless gases with very low reactivity.
Noble gases are chemically unreactive primarily because their valence electron shells are full (He: 2; others: 8), giving high stability and little tendency to form bonds.
Their physical behavior is governed by weak intermolecular (London dispersion) forces, producing cryogenic boiling points and increasing melting/boiling points down the group.
Only a limited number of noble gas compounds are known; heavier noble gases (especially xenon) show the most chemistry.
The periodic table group containing the noble gases (He, Ne, Ar, Kr, Xe, Rn, and sometimes Og).
Low-reactivity monatomic elements whose full valence electron shells make them resistant to chemical bonding.
The outer electron shell containing the maximum stable number of electrons (2 for helium, 8 for the others), which strongly reduces chemical reactivity.
A weak intermolecular attraction caused by temporary fluctuations in electron density, dominating noble-gas interactions.
A synthetic, highly unstable element considered part of group 18 by IUPAC, but with uncertain chemistry and physical properties.
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