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mass number definition

mass number

Physics, Chem. the number of neutrons and protons in the nucleus of an atom: the approximate mass of a given nucleus is obtained by multiplying the mass number by the fundamental unit of mass, 1.6605 × 10 grams ( the mass of C atom)

Webster's New World College Dictionary Copyright © 2009 by Wiley Publishing, Inc., Cleveland, Ohio.
Used by arrangement with John Wiley & Sons, Inc.

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