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atomic mass

[ uh-tom-ik mas ]
/ əˈtɒm ɪk ˈmæs /
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noun Chemistry.
the mass of an isotope of an element measured in units formerly based on the mass of one hydrogen atom taken as a unit or on 1/16 (0.0625) the mass of one oxygen atom, but after 1961 based on 1/12 (0.0833) the mass of the carbon-12 atom.

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Origin of atomic mass

First recorded in 1895–1900
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use atomic mass in a sentence

  • What is specially of interest is that the indicated atomic mass of each of the constituents is a whole number.

    Alchemy: Ancient and Modern|H. Stanley Redgrove
  • The best evidence that these particles are of atomic mass is furnished by their deflection in electric and magnetic fields.

    A Brief Account of Radio-activity|Francis Preston Venable

British Dictionary definitions for atomic mass

atomic mass

noun chem
the mass of an isotope of an element in atomic mass units
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for atomic mass

atomic mass

The mass of a given atom or molecule, expressed in atomic mass units. Compare atomic weight. See also mass number.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
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