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

On a day of firsts, 336 ended up being the magic number.

From BBC ● Jul. 10, 2026

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

From Barron's ● Jun. 27, 2026

You may start a trend among wealthy parents, making $76,000 the magic number.

From MarketWatch ● Jan. 8, 2026

The magic number: For Bierbaum, $20 is the magic number, a price where customers don’t think twice when they buy.

From The Wall Street Journal ● Dec. 6, 2025

Even today, a critical threshold in human organisations falls somewhere around this magic number.

From "Sapiens: A Brief History of Humankind" by Yuval Noah Harari

Related Words

• code
• confidential information
• key
• mystery