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M-shell

American  
[em-shel] / ˈɛmˌʃɛl /

noun

Physics.

  1. the third shell of electrons surrounding the nucleus of an atom and containing, when filled, 18 electrons having principal quantum number three.

Etymology

Origin of M-shell

First recorded in 1920–25

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.