- any of up to seven energy levels on which an electron may exist within an atom, the energies of the electrons on the same level being equal and on different levels being unequal.
- a group of nucleons of approximately the same energy.
- a scab on the surface of an ingot.
- a length of unfinished tubing.
- a pierced forging.
- a hollow object made by deep drawing.
verb (used with object)
verb (used without object)
Origin of shell
- a class of electron orbits in an atom in which the electrons have the same principal quantum number and orbital angular momentum quantum number and differences in their energy are small compared with differences in energy between shells
- an analogous energy state of nucleons in certain theories (shell models) of the structure of the atomic nucleus
Word Origin for shell
Old English sciell, scill, Anglian scell "seashell, eggshell," related to Old English scealu "shell, husk," from Proto-Germanic *skaljo "piece cut off; shell; scale" (cf. West Frisian skyl "peel, rind," Middle Low German schelle "pod, rind, egg shell," Gothic skalja "tile"), with the shared notion of "covering that splits off," from PIE root *(s)kel- (1) "to cut, cleave" (cf. Old Church Slavonic skolika "shell," Russian skala "bark, rind;" see scale (n.1)). Italian scaglia "chip" is from Germanic.
Sense of "mere exterior" is from 1650s; that of "hollow framework" is from 1791. Meaning "structure for a band or orchestra" is attested from 1938. Military use (1640s) was first of hand grenades, in reference to the metal case in which the gunpowder and shot were mixed; the notion is of a "hollow object" filled with explosives. Hence shell shock, first recorded 1915. Shell game "a swindle" is from 1890, from a version of three-card monte played with a pea and walnut shells.
1560s, "to remove (a nut, etc.) from a shell," from shell (n.). The meaning "to bombard with shells" is first attested 1856. To shell out "disburse" (1801) is a figurative use from the image of extracting nuts. Related: Shelled; shelling.
- The usually hard outer covering of certain animals, such as mollusks, insects, and turtles.
- The hard outer covering of a bird's egg.
- The hard outer covering of a seed, nut, or fruit.
- A set of electron orbitals that have nearly the same energy. Electrons in outer shells have greater energy than those in shells closer to the nucleus. Elements in the Periodic Table range from the lightest elements with electrons normally occupying one shell (hydrogen and helium) to the heaviest, with electrons in seven shells (radium and uranium, for instance). See more at atomic spectrum orbital subshell. See Note at metal.
- Any of the stable states of other particles or collections of particles (such as the nucleons in an atomic nucleus) at a given energy or small range of energies.
In addition to the idiom beginning with shell
- shell out
- in one's shell