K-shell

[ key-shel ]
/ ˈkeɪˌʃɛl /

noun Physics.

the first shell of electrons surrounding the nucleus of an atom and containing, when filled, two electrons having principal quantum number 1.

Origin of K-shell

First recorded in 1965–70
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019