magic number

American  

noun

Physics.

1. the atomic number or neutron number of an exceptionally stable nuclide.

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magic number British  

noun

1. physics any of the numbers 2, 8, 20, 28, 50, 82, and 126. Nuclides with these numbers of nucleons appear to have greater stability than other nuclides

2. chem a number of atoms that is particularly stable in certain types of compound that have clusters of the same type of atom

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magic number Scientific  

/ măj′ĭk /

1. Any of the numbers, 2, 8, 20, 28, 50, 82, or 126, that represent the number of neutrons or protons in strongly bound and exceptionally stable atomic nuclei. The existence of such stable nuclei is explained by assuming a shell structure for nucleons, much like the shell structure of electron orbitals around the nucleus.

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Etymology

Origin of magic number

First recorded in 1945–50

Example Sentences

See Examples For:

magic number

There’s a magic number that makers of everyday goods are obsessed with: $9.99.

From The Wall Street Journal ● Jul. 14, 2026

Duke’s Kraus came up with his magic number from research that tracked step counts.

From Barron's ● Jun. 27, 2026

Simon King, the BBC's lead weather presenter, says 15C tends to be the magic number.

From BBC ● Oct. 25, 2025

Read: Amazon’s stock comeback hinges on AWS hitting this magic number.

From MarketWatch ● Oct. 20, 2025

He had been in Hutterite colonies that had come near to that magic number and seen firsthand how things had changed.

From "The Tipping Point" by Malcolm Gladwell

Related Words

• code
• confidential information
• key
• mystery