mass number

noun

Definition of mass number 

: an integer that approximates the mass of an isotope and designates the number of nucleons in the nucleus

First Known Use of mass number

1923, in the meaning defined above

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The first known use of mass number was in 1923

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More Definitions for mass number

mass number

noun

Medical Definition of mass number 

: an integer that approximates the mass of an isotope and that designates the number of nucleons in the nucleus the symbol for carbon of mass number 14 is 14C or C14 — compare atomic mass

More from Merriam-Webster on mass number

Britannica.com: Encyclopedia article about mass number

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