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CHEM 121 Studioby Learn4Less · UBC CHEM 121

CHEM 121 glossary

Noble-gas configuration

The filled-shell configuration of a noble gas (He, Ne, Ar, Kr, …). In noble-gas notation the core is written as the preceding noble gas in brackets, followed by the valence electrons; main-group ions usually reach a noble-gas configuration.

Example

Bromine (Z=35Z = 35) is [Ar] 4s2 3d10 4p5[\mathrm{Ar}]\,4s^2\,3d^{10}\,4p^5, where [Ar][\mathrm{Ar}] stands for 1s2 2s2 2p6 3s2 3p61s^2\,2s^2\,2p^6\,3s^2\,3p^6. Gaining one electron gives BrX−\ce{Br-}, the same configuration as Kr.

See alsoCore electronElectron configurationIsoelectronicOctet rule