Magic number

From Fresh Dictionary

English

Noun

magic number

1. ((physics{{#if:|, {{{2}}}{{#if:|, {{{3}}}{{#if:|, {{{4}}}{{#if:|, {{{5}}}{{#if:|, {{{6}}}{{#if:|, {{{7}}}{{#if:|, {{{8}}}{{#if:|, {{{9}}}}}}}}}}}}}}}}}}})) the number of neutrons or protons in nuclei which are required to fill the major quantum shells, and thus produce exceptionally stable nuclei - 2, 8, 20, 28, 50, 82 & 126